The parts of speech are also known as lexical categories, and they are the groups of certain types of words based on their function in a sentence. They include nouns, verbs, articles, pronouns, conjunctions, adverbs, prepositions, and participles. Figures of speech are words or phrases that have a less literal meaning and are used for literary effect instead of for meaning. A list of many figures of speech are here: http://en.wikipedia.org/wiki/Figures_of_speech
Adjectives, verbs, and nouns are words or parts of speech.
Single verbs are used for formal speech or writing.
Verbs have their own part of speech.
Verbs need subjects, which can be nouns or pronouns.
Nouns and verbs and pronouns and adjectives and adverbs are parts of speech.
Can and relax are verbs.
Verbs are conjugated.
Verbs
Adjectives, Nouns, and Verbs are all parts of speech. So, the one thing that they have in common is that they're parts of speech.
They are verbs
The parts of speech are the nuts and bolts of language. You can talk about the functions of the parts of speech (nouns, verbs, adjectives, adverbs, prepositions) without any regard to the meanings of the words themselves. Figures of speech are creative uses of language in order to convey certain moods or meanings.