The second day of the week, coming after Monday and before Wednesday. The kanji '火' (ka) means fire, linking it to the planet Mars in some cultural contexts. It's typically a busy workday.

一(いち)週(しゅう)間(かん)の二(ふた)日(か)目(め)で、月(げつ)曜(よう)日(び)の次(つぎ)に来(く)ます。「火(ひ)」の字(じ)は火(か)星(せい)を表(あらわ)します。