熱があるんです。

heat; fever; temperature; zeal; passion; enthusiasm; mania; craze; rage

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

yes; yeah; uh huh; negative verb ending used in informal speech (abbr. of negative verb ending "nu"); abbr. of particle "no"; abbr. of particle "ni" (used especially when it precedes the verb "naru")

be; is