Learn Portuguese (Portugal): Eu sei que a mentira é o problema.

Eu sei que a mentira é o problema.

I know that the lie is the problem.

Breakdown of Eu sei que a mentira é o problema.

Questions & Answers about Eu sei que a mentira é o problema.

Why is "I know" eu sei? Is saber an irregular verb?

Yes! The verb saber (to know) is highly irregular in the "I" form. Instead of following the normal rules, the eu form becomes sei. Fortunately, the other present tense forms are regular: tu sabes, ele/ela/você sabe, nós sabemos, and eles/elas/vocês sabem.

Could I use eu conheço instead of eu sei in this sentence?

No. In Portuguese, there are two verbs for "to know". You use saber for knowing facts, information, or knowing that something is true (as in this sentence). You use conhecer when you are familiar with a person, a place, or an object (like knowing a friend or a city).

Do I really need the word que (that) here, or can I leave it out like in English?

You must keep it! In English, we often drop the word "that" and just say "I know the lie is the problem." In Portuguese, you cannot drop this connecting word. You must always use que to link the two halves of the sentence: Eu sei que...

The word problema ends in "-a". Why does it use the masculine article o?