Learn Finnish: Minä tulen suoraan uimasta. - I am coming straight from swimming.

This is the third infinitive in the elative case, which translates to 'from doing something'. Because the verb tulla (to come) implies movement away from an action, the activity you are coming from must take the 'from' ending -sta. We use the third infinitive base uima- and add -sta to get uimasta.

How do we build the uima- part from the basic verb uida?

To make the third infinitive, you start with the 'I' form of the present tense. For uida (to swim), that is uin. Drop the -n to get the stem ui-, and add the marker -ma- (or -mä- for front vowels). This gives you uima-, ready for its case ending.

Why does suoraan have a double vowel and an -n at the end?

The base word is the adjective suora (straight). To turn it into an adverb meaning 'directly' or 'straight' (as in 'straight from'), Finnish uses the illative case ending (the 'into' case). You lengthen the final vowel and add -n, turning suora into suoraan.

Why isn't there a word for 'am' in the Finnish sentence?