私はフランス語を専攻しようと決めた。

I; me; private affairs; personal matter; secrecy; selfishness

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

French (language)

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.

major subject; special study

if; when; and; with; particle used for quoting (with speech, thoughts, etc.); quoting particle; promoted pawn; indicates question (sentence end)

to decide; to choose; to determine; to make up one's mind; to resolve; to set one's heart on; to settle; to arrange; to set; to appoint; to fix; to clinch (a victory); to decide (the outcome of a match); to persist in doing; to go through with; to always do; to have made a habit of; to take for granted; to assume; to dress up; to dress to kill; to dress to the nines; to carry out successfully (a move in sports, a pose in dance, etc.); to succeed in doing; to immobilize with a double-arm lock (in sumo, judo, etc.); to eat or drink something; to take illegal drugs