1. The crowd was small.

2. The crow were deeply impressed by the concert.

3. The audience was large/big.
4. The audience were began to talk loudly.

5. The family is large/big.
6. The family are all well.

7. The committee is composed of 6 members.
8. The committee are having dinner.

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Are they all grammatical? Can we use both big and large? Do the four nouns have the same character? Crowd, audience, family and committee, I mean.

Correct ~~> 1, 3, 5, 7.

All the nouns are considered collective nouns: http://www.chompchomp.com/terms/collectivenoun.htm

Not all of the sentences are grammatical, and there are some differences in usage for the words "big" and "large." Let's go through each sentence and analyze them individually:

1. The crowd was small. (grammatical)
2. The crow were deeply impressed by the concert. (incorrect - "crow" should be "crowd")

3. The audience was large/big. (grammatical, "large" and "big" are both acceptable here)
4. The audience were began to talk loudly. (incorrect - "were" should be "was" and "began" should be used instead of "were began")

5. The family is large/big. (grammatical, "large" and "big" are both acceptable here)
6. The family are all well. (grammatical, "are" is used because "all" refers to the members of the family)

7. The committee is composed of 6 members. (grammatical)
8. The committee are having dinner. (incorrect - "committee" should be treated as a singular noun, so "is" should be used instead of "are")

As for the usage of "big" and "large," they can generally be used interchangeably in these contexts. Both words can mean "of considerable size," but there are subtle differences in usage. "Big" often emphasizes physical size, while "large" can refer to physical size as well as magnitude, importance, or number.

Regarding the four nouns (crowd, audience, family, and committee), they are different in nature and can have different characteristics:

- Crowd: Refers to a group of people gathered together in a particular place. It is typically treated as a collective unit.
- Audience: Refers to the group of people who are present to witness a specific event, such as a performance or presentation. It can be treated as a collective unit or as individual members.
- Family: Refers to a group of people who are related to each other by blood, marriage, or adoption. It is considered a collective unit but can also refer to individual members.
- Committee: Refers to a group of people who are appointed or elected to perform a specific task or make decisions. It is generally treated as a collective unit but can also refer to individual members.

In summary, while "big" and "large" can be used interchangeably in some cases, there are specific differences in usage. Additionally, each of the four nouns has its own characteristics and can be treated differently grammatically.