Learn Portuguese (Portugal): Às segundas-feiras, costumo matar insetos no jardim. - On Mondays, I usually kill insects in the garden.

In Portugal, it is standard to use the preposition a (combined here with the plural feminine article as to make Às) before days of the week to talk about a recurring habit. Às segundas-feiras translates to "on Mondays". Notice how both halves of the compound word get an -s to form the plural.

How does costumo matar translate to "usually kill"?

Instead of using a separate adverb for "usually", Portuguese often uses the verb costumar (to be in the habit of) followed by the infinitive of the main verb. So, costumo matar literally means "I am in the habit of killing". You conjugate costumar to match the person doing the action.

Why is there no word for "I" before costumo?

The -o ending of the verb costumo clearly shows that the subject is "I" (eu). As you may remember from earlier levels, Portuguese usually drops subject pronouns unless they are needed for emphasis or to clear up confusion.

Why is insetos spelled without a "c"?

You might sometimes see this word spelled as "insectos" in older texts or Brazilian Portuguese. However, under the modern Portuguese spelling agreement, silent consonants were dropped. Since the "c" is not pronounced in this word in Portugal, the correct standard spelling is now insetos.