What happened to the -ly ending?
We use the ‑ly ending to add to adjectives to convert them to adverbs. Thus, the adjective easy becomes the adverb easily, the adjective rapid becomes the adverb rapidly, and the adjective careful becomes the adverb carefully.
But many adverbs do not have the ‑ly ending. Some words have identical forms as adjectives and adverbs. Consider the word fast. It’s an adjective, as in the fast runner or the fast car. But it’s also an adverb. When describing Igor, our early grammarians grunted, Igor runs fast. They didn’t say, Igor runs fastly.
Think about the word straight. It’s an adjective, as in the straight line. But it can also act as an adverb when we say, We go straight to the point. We wouldn’t say, We go straightly to the point.
Interestingly enough, when you modify verbs with adverbs, those ending in ‑ly have the capacity to come before the verb. But most of those not ending in ‑ly have a hard time preceding the verb they modify. We cannot say, for example, Igor fast runs or We straight go to the point.
A final point on the ‑ly ending. Many people (especially sportscasters) do not distinguish between adjectives and adverbs. They just use the adjective form to perform double duty and serve as adverbs. Basically, they’ve excised the ‑ly adverb out of the language:
She swam that lap easy, don’t you think, Mark?
He hit that one soft, now didn’t he?
If these announcers cared about the language, they would find out that easy can indeed serve as an adverb, but its adverbial use is a colloquial one, as in take it easy. The swimming announcer should have said:
She easily swam that lap, don’t you think, Mark?
He hit that one softly, now didn’t he?