semana, noun:
week

Notice the use of the phrase entre semana meaning during the week.

los que salen entre semana
people who go out on weekdays

Sucedió un dia entre semana.
It happened on a weekday.

La semana is a case where the Spanish and English words bear no resemblance to each other. They don’t look alike because the English word comes from the Germanic side of English, whereas the Spanish word comes from the Late Latin septimana, week. The Latin word also gave birth to the word for week in the Romance languages: French la semaine, Italian la settimana, Portuguese a semana and Romanian săptămână.