交換【こうかん】
exchange, interchange, switching, reciprocity, barter, substitution, replacement, clearing (of checks, cheques)
換算【かんさん】
conversion (e.g. yen to dollars), change, exchange, translation (numerical)
引き換え【ひきかえ】
exchange, conversion
換気【かんき】
ventilation
乗り換え【のりかえ】
transfer (trains, buses, etc.), change, connection, switch (to another ideology, party, system, method, etc.), change, conversion, switching (stock), chromosomal crossover, crossing over
変換【へんかん】
change, conversion, transformation, transformation
乗り換える【のりかえる】
to transfer (trains), to change (bus, train), to change (to another ideology, party, company, etc.), to switch (to a different system, method, etc.), to move on to (e.g. a new love interest)
言い換える【いいかえる】
to say in other words, to put another way, to express in different words, to reword, to rephrase