彼の招待は受けざるを得ない。

he; him; his; boyfriend

indicates possessive; nominalizes verbs and adjectives; substitutes for "ga" in subordinate phrases; (at sentence-end, falling tone) indicates a confident conclusion; (at sentence-end) indicates emotional emphasis; (at sentence-end, rising tone) indicates question

invitation

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

to receive; to get; to catch (e.g. a ball); to be struck by (wind, waves, sunlight, etc.); to sustain (damage); to incur (a loss); to suffer (an injury); to feel (influence); to undergo (e.g. surgery); to take (a test); to accept (a challenge); to be given (e.g. life, talent); to follow; to succeed; to be descended from; to face (south, etc.); to be modified by; to obtain (a pawned item, etc.) by paying a fee; to be well-received; to become popular; to go down well

indicates direct object of action; indicates subject of causative expression; indicates an area traversed; indicates time (period) over which action takes place; indicates point of departure or separation of action; indicates object of desire, like, hate, etc.

to get; to earn; to acquire; to procure; to gain; to secure; to attain; to obtain; to win; to understand; to comprehend; to receive something undesirable (e.g. a punishment); to get (ill); to be able to ..., can ...