How can we using was and is in tenses in English grammar?

In English grammar, "was" is used in the past tense to indicate an action or state that occurred in the past. For example, "She was happy yesterday."

On the other hand, "is" is used in the present tense to indicate an action or state that is currently happening or is generally true. For example, "He is studying for his exam."

To use both "was" and "is" in tenses, you can create sentences that show a change or transition from the past to the present. For example, "She was sad last week, but now she is happy." This sentence shows a shift from a past state of sadness to a present state of happiness.