When do you use is or was in a sentence?

Answer 1

Both is and was are forms of the verb to be.

Is represents the third-person singular (he, she it) in the present tense.

Was represents the third-person singular (he, she, it) in the past tense.

Example:

The boy is late for school, and he was also late yesterday.

As a helper verb:

The dog is eating his food now, but he was eating my sandwich a minute ago.

Answer 2

Use "is" in a sentence when referring to something in the present or the general truth. Use "was" when referring to something in the past. For example, "He is happy now" uses "is" for the present moment, while "He was happy yesterday" uses "was" for the past.