試験のことで頭がいっぱいだ。

examination; test; study; trial; experiment

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

thing; matter; incident; occurrence; event; something serious; trouble; crisis; circumstances; situation; state of affairs; work; business; affair; after an inflectable word, creates a noun phrase indicating something the speaker does not feel close to; nominalizing suffix; pretending to ...; playing make-believe ...; alias; aka; nickname; alternative name; also known as

indicates location of action; at; in; indicates time of action; indicates means of action; cause of effect; by; and then; so; indicates continuing action; indicates certainty, emphasis, etc.

head; hair (on one's head); mind; brains; intellect; leader; chief; boss; captain; top; tip; beginning; start; head; person; top structural component of a kanji

indicates sentence subject (occasionally object); indicates possessive (esp. in literary expressions); but; however; still; and

amount necessary to fill a container (e.g. cupful, spoonful, etc.); drink (usu. alcoholic); full; one squid, octopus, crab, etc.; one boat; fully; to capacity; a lot; much; all of ...; the entire ...

be; is; indicates past or completed action; indicates light imperative