“All” OR “All of”?

✔️If you use "all of" before words like

"us," "you," "it," "him," and "her" (i.e., personal pronouns), you will be correct.

For example:
•All of us = All of us are going to the party.
All of them = All of them are working overtime.

✔️If you use "all" before nouns, you will be correct.

For example:
•All the cheese = Who ate all the cheese? (Many people will say or write — Who ate all OF the cheese? But using “of” is not necessary.

•All the soldiers = All the soldiers will return home this winter. (Again, it’s not necessary to use “of” in this sentence — All OF the soldiers will come home this winter.)

✔️The Grammar of "All"

"All" as a determiner preceding a noun:

When used by itself before a noun, the word "all" is classified as a determiner. For example:

all men
all the students

Using "all" as a determiner is preferable to using "all of" because it saves a word. (NB: Sometimes, the noun is preceded by "the." Sometimes, it isn't.)

"All" as a determiner preceding a pronoun:

Using "all" as a determiner before a personal pronoun is usually wrong. For example:

all we
all they

The word "of" is required to avoid a reading stutter. Look at these fuller examples:

All we believe.
(Native English speakers would interpret this as "everything that we believe" and not "everybody believes.")

All they are thinking.
(Native English speakers would interpret this as "everything that they are thinking" and not "they all are thinking.")

✔️The Grammar of "All Of"

"All" as an indefinite pronoun preceding a noun:

When used in the phrase "all of," "all" is classified as an indefinite pronoun. It is perfectly acceptable to use "all of" before a noun. For example:

all of the men
all of the students