1. dependent/ subordinate clauses
(1) 4 types: noun, adjective (relative), adverb, that

(2) Noun clause
sub- What you do in your free time is your business.
sc- Tom isn't what you'd called friendly.
obj- She said (that) she was sorry.
obj of prep- I don't worry about what others think.
obj of v- I really want to believe that tomorrow will be better.

(3) adjective clauses
a. identifying (no commas)
b. non-identifying (commas)
c. situational (commas)
- The girl who sold me the car said it was hers.
- My high school English teacher, who is retired and now lives in Florida, sent me a postcard.
- I brought myself a motorcycle for my birthday, which made my wife crazy.
that→用在特定a. which→用在不特定b.

(4) Adverb clauses
目的：Show a relationship e.g. contrast, condition, reason, time
Although he practiced everyday, he didn't win.
If you help me pass this test, I'll buy you lunch.
I lent her my notes because she missed too many classes.

When my mother, who was only 18 when she had me, told me I should wait until I got older to marry Lucy, I knew she was really happy I met the right person.

source

tenses

2. if條件句

3. could/would/should have