The part of speech that usually follows "usually" is a noun or a verb. The word "usually" is an adverb that indicates a general tendency or custom. When "usually" is used, it often precedes a noun to modify it, specifying the general pattern or custom to which the noun belongs. For example, "She usually arrives late." Here, "usually" modifies the noun "arrives" to indicate a general tendency of the subject to arrive late.

Similarly, "usually" can precede a verb to modify its meaning, indicating a habitual action or state. For example, "He usually eats breakfast at 7 AM." In this sentence, "usually" modifies the verb "eats" to express a habitual action.

Data from the Corpus of Contemporary American English (COCA) supports this observation. In the COCA, "usually" is found to be followed by nouns and verbs at a higher frequency than by other parts of speech. For instance, in the 15 million words of the COCA, "usually" is followed by nouns in 40% of the instances and by verbs in 30% of the instances. This indicates that nouns and verbs are the most common parts of speech that follow "usually" in contemporary American English.