弟はこれまでテニスで負けたことがありません。

younger brother; little brother; kid brother; pupil; apprentice

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

this (indicating an item near the speaker, the action of the speaker, or the current topic); this person (usu. indicating someone in one's in-group); now; here; I (me); certainly

until (a time); till; to; up to; to (a place); as far as; to (an extent); up to; so far as; even; only; merely

tennis

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.

to lose; to be defeated; to succumb; to give in; to surrender; to yield; to be inferior to; to break out in a rash due to (e.g. lacquer, shaving, etc.); to reduce the price; to lower the price; to give a discount on

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

to be (usu. of inanimate objects); to exist; to live; to have; to be located; to be equipped with; to happen; to come about