Is "deep" an adjective or adverb?

Question

She worked quickly but without hurry. She put an old apron to cover her clothes. In the basement she found a jelly jar with a top and carried it out to the carriage house where the tools were kept. In the chickenyard she caught a little pullet, took it to the block and chopped its head off, and held the writhing neck over the jelly jar until it was half full of blood. Then she carried the quivering pullet to the manure pile and buried it deep. Back in the kitchen she took off the apron and put it in the stove and poked the coals until a flame sprang up on the cloth. She washed her hands and inspected her shoes and stockings and wiped a dark spot from the toe of her right shoe.

(John Steinbeck, East of Eden)

When I encounter the type of structure, I rather feel deep is an adjective – Predicative adjective over the object - than an adverb. Is this right reading?

Answer 1

In principle, deep is an adjective (modifies nouns), and deeply is an adverb (modifies verbs). In practice,

He cut deep into something. (about 2190 results in Google Books)
He cut deeply into it. (1030)

By which you can see that native speakers tend to ignore that principle when the verb is being used "actively". But when it's just a "passive" past participle, we invariably follow the rules...

He was deep hurt (1)
He was deep wounded (4)
He was deeply hurt (55000)
He was deeply wounded (20400)

Also note that in some constructions that might superficially look like "adverbial" usages, the word is actually part of an adjectival "modifier of location". We use the simpler form there as well...

He walked deeply into the forest. (38)
He walked deep into the forest. (7390)

---

In OP's example, deep is used adjectivally as per the above (it's telling us where the chicken was buried). It would be perfectly grammatical - if somewhat less common - to use deeply there (in which case the emphasis would be on how she buried it, not where).

---

This use of superficially adjectival forms in adverbial contexts is quite common in English. I can't think of an example where the difference between deep/deeply would be perceived as changing the meaning, but this certainly occurs with other words. For example...

1:He acts bad.
2:He acts badly.

...where in the absence of any other contextual information, we naturally tend to assume that #1 means he acts like a bad person, whereas #2 is likely to be interpreted as he's not good at acting.

Answer 2

Deep is an adjective, a noun (used with the definite article), and an adverb. In that case, it is an adverb and it means "far down or in; deeply."

traveling deep into the countryside.

Answer 3

Deep can be both an adjective and an adverb. There are some adverbs that have two forms, each with a difference in meaning. One of the examples is "deep". Example: * They buried the treasure deep underground. (deep as an adverb means "a long way down") * He is deeply depressed. (deeply means "very")