What’s the difference?

There + be: is an “expletive” structure. It does not have a meaning on its own

It introduces the idea that something is in a particular place. The form of the sentence is:

There + be (is, are, was, were, has/have/had been) + subject + place.

• There is a good talk show on TV right now.
• There are two people waiting for you in the hall.
• There has been a lot of noise in the street.

Their: a possessive adjective (like my, our, your, his, her, its) that comes before nouns to show the ownership of  something to a group of people or things

• This is their house. (= The house belongs to them.)
• Their company is a successful one. (= the company that belongs to them)
• Have you been to their restaurant? (= the restaurant that belongs to them)

They’re: a short form of They are

• They’re our dear friends. (They are)
• They’re preparing for the party at the moment. (They are)
• Did you know that they’re not coming tomorrow? (they are)

Its (without apostrophe): a possessive adjective (like my, our, your, their, his, her) that comes before nouns to show the ownership of  something 

• The cat moved its tail. (= the tail belongs to the cat)
• I bought this house because I liked its design. (= the design of the house)
• Each software has its hiccups. (= hiccups caused by the software)

It’s (with apostrophe): a short form of it is or it has

It is: when followed by a noun, adjective, or verb-ing 

• It’s my book. (followed by a noun)
• It’s hot here. (followed by an adjective)
• It’s going to be hot tomorrow. (followed by verb-ing)

It has: when followed by a past participle verb (verb 3)

• It’s been a long time since I last saw them. (= It has been …)

Than is used in comparison.

It connects the two people or things compared with comparative adjective.

• Tom is taller than Tim.
• Reading a story is more interesting than watching a movie.

Then is an adverb that has different meanings.

       Meaning 1: “next” or “the next step”

• She got ready, then she called a taxi.

       Meaning 2: “in that case”

• If you like this ice-cream, then I’ll bring you some more.

       Meaning 3: “at that time”

• I wanted to see you last night. What were you doing then?

Both of them are used to indicate time.

Since is used with point of time in the past.

It is used with time expressions that refers to a past time like: 6 o’clock, Saturday, January, 2000, I was young, …

• He has worked for this company since 2015.

For is used for a period of time (duration) in the present, past or future.

It is used with time expressions like: 2 hours, 3 days, 3 months, years, ages, a long time, …

• He has worked for this company for 6 years. (He still works for the company.)
• She lived in this house for 5 years. (She no more lives in this house.)
• We will stay with you for 2 weeks. (future)

Both will and be going to are used to express simple future.

Will is used to talk about unplanned actions – actions that we decide to do at the time of speaking. 

• The box looks heavy. I‘ll help you to carry it.

We also use will to talk about promises, hopes, threats, warnings, etc.

• I will bring you a sandwich from the canteen. 

Be going to is used to talk about planned events in the near future.

• They are going to move to another city next month.

Both will and be going to can be used to talk about predictions, but be going to is more used when the prediction is based on knowledge or evidence.

• I think it will snow in the evening.
• The sky is cloudy. It‘s going to rain soon.

All four words are demonstratives. They are used to point to people, things or places.

Near + Singular: This

Near + Plural: These

• Here you are!. You may use this pen.
• I like these doughnuts.

Distant + Singular: That

Distant + Plural: Those

• Can you see that car over there? It’s mine.
• What are those men doing in the street at this time?

Whose (without apostrophe): can be 

1. a relative pronoun to introduce a relative clause of possession 

• I met the lady whose daughter won the first prize in the reading competition.

      2. a question word to ask about possession

• Whose glasses are these?

Who’s (with apostrophe): short form of Who is or Who has

• Who’s your teacher? (= Who is)
• Who’s talking? (= Who is)
• Who’s written this memo?  (= Who has)

Both who and whom are relative pronouns used to refer to people (not things).

Who can be used for both subjects and objects. 

Whom can be used for objects only.

• The architect who designed my house is my closest friend. (subject of the relative clause, so we cannot use whom here)
• Is this the doctor who (or whom) we visited yesterday. (object of visited)
• This is the author who (or whom) I told you about. (object of the preposition about)

Note: We cannot use who immediately after a preposition. 

• This is the footballer about whom I told you. (NOT about who)

We use like to express similarity;

1. with nouns, pronouns, and ing forms

• He acts like a hero. (He is not a hero.)

2. with verbs of senses: feel, look, smell, taste

• It looks like a duck. (It’s not a duck.)

We use as to say what someone or something really is.

• He works as a project manager. (He is a project manager.)

Which introduces a nonrestrictive clause. In other words, the clause can be removed without changing the meaning of the sentence.

Nonrestrictive clauses provide additional information about the nouns they introduce.

• The copying machine, which we use to copy confidential documents, is in the principal’s office.

Using which in this sentence implies that we have only one copying machine. The which clause only adds information about it.

It is enclosed between two commas, and it can be left out without changing the meaning.

We cannot use that in nonrestrictive clauses.

That introduces restrictive clauses that limit the nouns they refer to.

Restrictive, or defining clauses, are important to specify the noun, so deleting them will change the meaning of the sentence. 

• The copying machine that we use to copy confidential documents is in the principal’s office.

This sentence means that we have more than one copying machine, but the one in the principal’s office is the one we use to copy confidential documents.

No commas are used to enclose defining clauses.

Which can be used instead of that in restrictive clauses.

Summary:

⇒⇒ When commas are necessary: use which only.

⇒⇒ When commas are unnecessary: use that or which.

Too and very are adverbs that come before adverbs and adjectives.

Too means “more than enough.” It usually implies a negative result.

Very emphasizes the adjective/adverb; it makes the adjective/adverb stronger.

• This tea is too sweet for me. (I can’t drink it because it has more sugar than I can take.)
• This tea is very sweet. (It emphasize the adjective “sweet.”)

• He works too hard. (He works much harder than is necessary.)
• He works very hard. (It emphasize the adverb “hard.”)

Do not use too to emphasize adjectives/adverbs.

• This cake is very delicious. (NOT too delicious)
• She sings very beautifully. (NOT very beautifully)

With some verbs such as like, dislike, doubt and hope, we use very much (NOT too much) to emphasize the verb.

• I like ice-cream very much. (NOT too much)

Note: The expression “too good to be true” means that it is so good or impressive that it is difficult to believe.

Both when and if are used to express condition.

But the meaning is a little different.

We use when to show that we are certain that something will happen.

• We will serve the food when you arrive. (We know that they will arrive; maybe they are on their way.)

We use if when we are not certain that something will happen.

• I will cook more food if more people decide to come. (I am not sure if more people will decide to come.)

If Clauses

Both of them modify noncount nouns.

“Little” means “almost none.”

I had little coffee in the pantry, so I couldn’t make a cup for my friend.

“A little” means “some, not much.”

There was a little sugar in the pantry, but it was enough to make a small cake for my daughter.

Count and Noncount Nouns

Both of them modify count nouns.

“Few” means “almost none.”

Few people showed up, so the lecture was cancelled. (almost nobody attended)

“A few” means “some but not many.”

A few people attended the lecture; the discussion was fruitful. (some people attended, but not many)

Count and Noncount Nouns