Breakdown of Se hai mal di testa, resta a letto.
a
to / at
il letto
the bed
restare
to stay, to remain
se
if
Questions & Answers about Se hai mal di testa, resta a letto.
Could I start this sentence with siccome instead of se?
Only if you want to change the meaning! siccome means "since" or "because" and states a known cause (Since you have a headache...). se means "if", which sets up a condition (I don't know if you have a headache, but if you do...).
I thought the "tu" form of restare was resti. Why is it resta here?
Because this is a command (the imperative mood), telling someone what to do. For regular -are verbs like restare, the informal tu (you) command ends in -a, while the normal present tense ends in -i.
Why isn't there an article before mal di testa?
Why is "in bed" translated as a letto instead of "in letto"?
In Italian, the fixed expression for being in bed or going to bed uses the preposition a without any article (a letto). It's one of those short prepositional phrases that's best to memorize as a single chunk.