Pronunciation guide: IPA symbols, stress and word endings

θ	thin	ð	this	ʃ	she	ʒ	measure
tʃ	church	dʒ	judge	ŋ	sing	j	yes

p b t d k g f v s z h m n l r w sound as in ordinary English spelling.

ˈ main stress, before the stressed syllable: /ˈwɔːtə/ water · ˌ lighter (secondary) stress: /ˌʌndəˈstænd/ understand
ː a long vowel · (r) an r said only in accents that pronounce it (most American, Scottish, Irish)

-s / -es (plurals; he/she form of verbs): /s/ after voiceless sounds (cats), /z/ after voiced (dogs), /ɪz/ after s, z, sh, ch, j sounds (buses, watches). Spelling: -es after s, x, z, ch, sh; consonant + y → -ies (city → cities).
-ed (past): /t/ after voiceless sounds (walked), /d/ after voiced (played), /ɪd/ after t or d (wanted). Spelling: love → loved, stop → stopped, carry → carried.
-ing: make → making, run → running, see → seeing.
Irregular: go, went, gone · be, was, been · see, saw, seen · man → men · child → children · mouse → mice.
Older (King James) forms: -eth = -s (he loveth = he loves) · -est with “thou” (thou lovest) · spake = spoke.

unknown

UK /ʌn(ˈn)əʊn/ · US /ʌnˈnoʊn/ adjective, noun

Forms unknowns

adjective (sometimes postpositive) Not known; unidentified; not well known. “The concept has existed since times unknown.”
noun (algebra) A variable (usually x, y or z) whose value is to be found.
noun Any thing, place, or situation about which nothing is known; an unknown fact or piece of information.
noun A person of no identity; a nonentity.

Synonyms

From Middle English *unknowen, *uniknowen, uniknowe, from Old English unġecnāwen (“unknown”), equivalent to un- + known.

Sources: Wiktionary · WordNet 3.0 · Webster’s 1913 — from the Wiktionary entry “unknown”, CC BY-SA 4.0. Details

Sanskrit dictionary entries whose meaning includes “unknown” (best matches first).