1. hence, thus, then, so, therefore

Hence and thus have the same basic meaning and are often interchangeable. However, there is a slight difference. Hence usually refers to the future. Thus usually refers to the past. It is often used to indicate a conclusion.
e.g.
* Both sides played well, thus no winner was declared.
* The situation is getting more and more complicated. Hence we will have to proceed with caution. (NOT Thus we will have to proceed with caution.)

So and then
There is a difference between then and so. Then is used when one speaker replies to another. So can be used in both ways.
e.g.
* ‘The last bus has gone.’ ‘So/ then we will have to walk.’ (Two speakers)
* ‘The last bus has gone, so we will have to walk. (NOT ‘The last bus has gone, then we will have to walk’) (Same speaker)

**Therefore is common in mathematical proofs.**   

e.g.
She was therefore unable to find a solution.

2. x year period, x years period, x-year-period and x-year-old

reference of hyphen rules
reference of x year period vs x years period

• If the target which we are talking about is singular then it should be x year period, since we're stating the x yehow to write addressar as 1 time (a period, a x year period), otherwise, it will be written as x years period
  e.g. "The maps illustrate the changes of the same area in Someland over a 20 year period."

• The use of x-year-period can be treated as what's called "compound adjective"

• Hyphens are often used to tell the ages of people and things. A handy rule, whether writing about years, months, or any other period of time, is to use hyphens unless the period of time (years, months, weeks, days) is written in the plural form
  e.g. "We have a two-year-old child."

3. Golf vocabs

Higher number, worse score

4. on the west of, in the west of, and to the west of

• on the west of
  It means the area is located at the west and bordered with the adjacent areas.
• in the west of
  The area is located at the west and is belonging to the target.
• to the west of
  The area is located at the west and is neither bordered with nor belonging to the target.

5. immigrate vs emigrate

• Immigrate indicates "come-in", which means the person goes into another country
• emigrate stands for "exit", if often used with the preposition from, e.g. Arnold Schwarzenegger emigrated from Austria to the United States.

https://www.grammarly.com/blog/emigrate-immigrate/
Immigrate begins with the letter I. If you associate I with “in,” you can easily remember that immigrate means to move into a different country. Emigrate begins with an E, so if you associate it with exit, you’ll remember that it means to leave your home country.

xuan's quotes from Udemy study note
https://www.udemy.com/course/ielts-7-plus-ielts-preparation/learn/lecture/10300646#notes
Emigrate can be understood as "exit", which is often used with the preposition "from", for example, Arnold Schwarzenegger emigrated from Austria to the United States, whereas immigrate is more likely to be related to "come-in" since it contains the letter "I", therefore, we can say, "Many young adults would love to immigrate to a foreign country."

6. complex, compound, and how to

references:
https://linguaholic.com/linguablog/is-with-which-correct-grammar/
https://www.theschoolrun.com/what-is-an-embedded-clause
https://www.englishforums.com/blog/which-means-how-to-use-it/

There are four sentence variations according to forms: simple, compound, complex, and compound-complex sentences.

• Simple sentence
  A simple sentence, also called an independent clause, contains at least one subject and one verb which forms a complete thought.

• Compound sentence
  Compound sentences are composed of at least two independent clauses that can stand separately.

• Complex sentence
  sentences composed of one independent clause and a minimum of one dependent clause fall under the complex type
  Complex sentences are conjoined by subordinate and correlative conjunctions like although, unless, no only…but also, and neither…nor.

• Compound-Complex
  This type of sentence utilizes both subordinating and coordinating conjunctions, which may also be replaced by semicolons.
  compound-complex sentences are made up of one or more independent clauses and one or more dependent clauses.

Examples:

1. simple sentence

I am. Babies cry. He left.
He struck the man with the bat, with which his son uses for playing baseball.

In the simple sentence above, the word bat is the object of the instrumental preposition with.

2. compound sentence

• A compound sentence, once again, is formed by combining two or more independent clauses with coordinating conjunctions.

• Coordinating conjunctions are mnemonically known as the FANBOYS (i.e., for, and, nor, but,
  or, yet, so).

• Compounded sentences necessitate a comma before the coordinating conjunction to mark the clausal segregation.

For example

The Akkadians ruled Mesopotamia for two centuries, and they successfully promoted bilingualism with which reinforced the symbiotic relationship among people.

the phrase with which and all other additional words refer back to the noun, bilingualism, and function as an adjective in the sentence.

3. complex sentence
   A complex sentence is a mixture of one independent clause and one or more subordinate clauses that are attached by either a subordinating or correlative conjunction.

For example

Although most people think caterpillars are cringe-worthy, my brother takes care of one as a pet at home, with which he even keeps in his room and feeds regularly.

Similar to the examples in simple and compound sentences, all lexical constituents after with which are used to modify the word caterpillar.

4. Compound-complex Sentence
   As the term implies, a compound-complex sentence is a combination of compound and complex sentences.

   The quick and easy way to identify this sentence pattern is to look for at least one coordinating conjunction and one subordinating conjunction in the sentence.

For example

Because Josh has always been a huge fan of Kurt Cobain, he has collected all of Nirvana’s albums, and he even visited Kurt’s old house in Seattle back in 2005.

7. The clause

reference
https://www.chompchomp.com/terms/clause.htm

8. Restrictive Relative Clauses and Non-Restrictive Relative Clauses

• Restrictive Relative Clauses
  Restrictive relative clauses give information that defines the noun—information that’s necessary for complete identification of the noun. Use “that” or “which” for non-human nouns; use “that” or “who” for human nouns. Do not use commas.
  e.g.

  I like the paintings that hang in the SASB North lobby.

• Non-Restrictive Relative Clauses
  This type of relative clause merely provides extra information. The information may be quite interesting and important to the larger conversation, but it is not essential for precise identification of the noun. “That” cannot be used as a relative pronoun in a non-restrictive relative clause. Commas are always used at the beginning and end of this type of relative clause.
  e.g.

  I’m planning to grow roses, which I find quite beautiful.

9. could be vs would be

"Could" is used to say that an action or event is possible. Would is used to talk about a possible or imagined situation, and is often used when that possible situation is not going to happen.

10 if vs whether

Whether and if are often interchangeable, but sometimes only one of them is correct. To avoid any danger of mistake, use if to introduce a condition and whether when there are two alternatives possible. If is used to introduce a condition.

11 organize vs organise

Organise and organize are different spellings of the same word. Organize is the preferred spelling in the U.S. and Canada, and organise is more common outside North America. This extends to all the word's derivatives, including organized/organised, organizing/organising, and organization/organisation.

12 practise vs practice

In American English, practice is always right. In British English, whether practice or practise is the correct choice depends on its role in the sentence. ... You spell the verb form, practise, with an S. However, if you are referring to the the doctor's business, you can use the noun form, practice with a C.

13 Dashes & Parentheses

• A dash signals an abrupt break in thought. It can be seen as “surprising” the reader with information.

  If used judiciously it can mark a longer, more dramatic pause and provide more emphasis than a comma can. If overused, it creates an impression of haste and carelessness and can diminish cohesion in your paragraphs.

  There has been a huge rise in adult depression globally within the last ten years - and "success within work can have a positive effect on this".

• Parentheses also signify a break in thought, but they mark an addition of information rather than an interruption like dashes do. Rather than a surprise (like dashes), parentheses are a gentler insertion in your sentence.

  For example, if a person works hard on a task(and gives 100% focus to it) then they will have the chance of gaining new knowledge.

i.e., e.g., and etc.

https://proofreadmyessay.co.uk/writing-tips/e-g-vs-i-e/
https://bigwords101.com/2014/blog/etc-e-g-i-e-whats-up-with-those/

• i.e. - id est, means that is
• e.g. - exempli gratia, means for example
• etc. - et cetera, means and others, it is often used at the end of a list in text.
  The above abbreviations, which are all Latin phases, are now commonly used in academic writing

14 About parentheses

parentheses

15 difference between houses

• Single-family house, townhouse

Perhaps the most obvious difference between a townhouse vs. single-family home is the structure. Townhouses are attached to one another, with each having at least one shared wall with adjacent townhomes. Single-family homes are freestanding, typically on a plot of land that also belongs to the homeowner. Townhome owners also own the parcel of land on which the townhouse stands, which often consists of small front and backyard areas.

Townhomes, which are generally multilevel residents attached to other residences, are defined by ownership—which includes the land the home is situated on, front- and backyard areas, and exterior.

• Condominiums

Condominiums provide the most hands-off approach to homeownership and are physically indistinguishable from rental apartments.

• Detached homes

Detached homes, however, often provide owners with the most freedom when it comes to improving the structures or the land that comes with them, but they also tend to lack many of the amenities.

16. About Personal Name

personal name

17 phone number

• When writing phone numbers, separate
  each group of digits with a hyphen ( - ):
  520-447-9821.

• Occasionally, people say the last four
  digits of phone numbers like two normal
  two-digit numbers: 447-9821 = four - four -
  seven, ninety-eight twenty-one.0

• The area code is sometimes written inside
  parentheses ( ) and without a hyphen:
  (520) 447-9821.

• Extensions are part of many office phone
  numbers. To show an extension number,
  the abbreviations Ex, Ext, or X are often
  used: 520-447-9821, Ex 213 (or Ext 213 or
  X 213).
  If extension numbers have three digits,
  they're usually said as single-digit numbers:
  X 517 = extension five - one - seven.
  If extension numbers have two digits,
  they're said with single digits or like
  normal two-digit numbers: extension 15 =
  extension one - five OR extension fifteen.

18 date format, ordinal number and month

• date format
  👍 6 Sept
  👍 6 September
  👍 6 September 2019
  👍 6th September 2019
  👍 the 6th of September 2019
  👍 the 6th of September, 2019
• ordinal number
  1: first, 1st
  2: second, 2nd
  3: third, 3rd
  4: fourth, 4th
  5: fifth, 5th
  6: sixth, 6th
  7: seventh, 7th
  8: eighth, 8th
  9: ninth, 9th
  10: tenth, 10th
  11: eleventh, 11th
  12: twelfth, 12th
  20: twentieth, 20th
  21: twenty-first, 21st
  22: twenty-second, 22nd
  23: twenty-third, 23rd
  24: twenty-fourth, 24th
  30: thirtieth, 30th
  100: one hundredth, 100th
  1000: one thousandth, 1,000th
  1 million: one millionth, 1,000,000th
  1 billion: one billionth, 1,000,000,000th
• month
  January Jan.
  February Feb.
  March Mar.
  April Apr.
  May May
  June Jun.
  July Jul.
  August Aug.
  September Sep. or Sept.
  October Oct.
  November Nov.
  December Dec.

19. Birthday

I was born on (the) 18th (of) August 2006 (said two thousand and six)
I was born at 16:25 on the 18th (of) August 2006
I was born at twenty-five past four on the 18th (of) August 2006
I was born in the afternoon of the 18th (of) August 2006
I was born in the early evening of the 18th (of) August 2006
I was born on the 1st of June, 1961

both in and on

Born in:
born in + year — I was born in 1980.
born in + month — I was born in October.
born in + place — I was born in Guadalajara.
Born on:
born on + day — I was born on Saturday.
born on + date — I was born on the 4th of July.

30 stigmatize 污名化

20 Main differences between British and American English