Learn Finnish: Myös suullinen sopimus on laillinen. - An oral agreement is also legal.

The adjective suullinen comes from the noun suu (mouth). Adding the -llinen suffix is a very common way to turn a noun into an adjective, giving it the meaning of being related to or having the quality of that noun. Therefore, something related to the mouth becomes oral or verbal.

What is the root word of laillinen and why does its spelling change?

The root is the noun laki (law). When we add the -llinen suffix, the word undergoes consonant gradation. The weak grade causes the k to disappear, giving us the stem lai-. Adding the suffix then creates laillinen, meaning legal.

Can I put myös after the verb, similar to how we say is also in English?

In Finnish, the adverb myös usually goes immediately before the word or phrase it emphasizes. Placing it at the very beginning emphasizes the entire phrase suullinen sopimus (an oral agreement), drawing a direct comparison to a written one. Putting it later in the sentence would sound unnatural here.

I recognize the start of the word sopimus. Is it related to the verb sopia?

Yes, it is formed directly from the verb sopia (to agree or to fit). The suffix -mus is frequently used to turn a verb into a noun, transforming the action of agreeing into the noun for an agreement or contract.