This specific reference material tells you how to pronounce a word, and
a word's part of speech.

Assuming you had to choose between:

The answer is dictionary.

This is the only reference material which will indicate a word's pronunciation (usually using phonetical characters and separating the syllables) as well as information like its part of speech (noun, pronoun, adjective, verb, adverb, preposition, etc.); alongside, obviously, its definition(s).

For example, this is what you can find if you search the word "dictionary" (the pronunciation and part of speech are underlined):

Dictionary. noun. \ ˈdik-shə-ˌne-rē \ : A reference source in print or electronic form containing words usually alphabetically arranged along with information about their forms, pronunciations, functions, etymologies, meanings, and syntactic and idiomatic uses.

butt

explanation:

technical documents should be clear and precise. basically, clarity is the key element in a successful technical document.