What is the meaning of -de?

forms ordinal numbers from cardinal numbers; -st, -th, -nd

forms adverbs from numerals with a meaning of "a certain number of times" or "(in) a certain number of places;" equivalent to English -ce in once, twice, thrice

appended to an adjective, making a feminine noun referring to the size of the quality referred to by the adjective, cognate to

appended to the stem of a verb, yields a feminine noun which refers to the object of such a verb

forms adverbs from numerals indicating a number of times

at a specific place or time

when, where, whenever, at that time

alternative form of -the (ordinal suffix)

used to derive verbs from roots

used to form the first and third person singular preterite indicative of some class I and class III weak verbs

used to form adjectives from nouns, denoting quality, kind, origin, or material

-'s, of (but with the order switched); attached to nouns to mark the genitive case

that, who; attached to nouns, adjectives, verbs, or phrases to mark them as attributive

-ing; attached to verbals to form a noun phrase or nominal expression

-er; attached to verbs to form agent nouns

attached for emphasis

so much that (attached to the main verb)

attached to the main verb to indicate that the subsequent verb or adjective is used as an adverb of the main verb

intensifier that attaches to adverbs, used especially in contexts of surprise

used in certain contexts to soften speech or make it more polite

again, anew

forms ordinal numbers from cardinal numbers

a suffix that forms the singular of the past tense of weak verbs

indicates second person in inversion, substituting or supplementing gij; you

forms abstract nouns from adjectives

added to a verb to form a noun indicating the place of the action

second-person singular present active imperative of -dō

creates the past tense of weak verbs in the first conjugation

used to form locative of nouns

indicates time; at

when

over

Source: wiktionary.org