All those sentences need an adjective: He is nice. In every case, an adverb comes after the verb and in every case that’s obviously the wrong choice. Think about these sentences: He is nicely. The most common copular verb is “be,” along with its conjugated forms including “is,” “am” and “are.” Native English speakers understand intuitively that “be” works differently from other verbs. They’re called copular or linking verbs, and they either refer back to the subject or deal with the senses. There’s a whole category of verbs that take adjectives, not adverbs, as their complements. That’s true, but there’s more to the story.

We were all taught in elementary school that adverbs modify verbs and adjectives modify nouns: Happy adults sing happily. They should have used the adjective “positive.” To understand why requires a quick look at which verbs are modified by adverbs. Well-informed people can disagree about whether the Times should have used “positive” instead of “positively.” But in my view, they made a mistake. So “happily” makes a good test of whether the New York Times’ sentence required an adverb or an adjective. The adjective “happy” would seem like a better choice - many adults feel happy - than the adverb. But what if they wrote instead: “Many older adults feel happily about their lives”? The structure is identical, but suddenly the grammar seems wrong. That sentence probably sounds as acceptable to you as it did to the Times editors.

“Many older adults said they feel positively about their lives,” the New York Times reported recently.

What is the adverb in this sentence