Learn Turkish: Su buzun altında akar. - The water flows under the ice.

The root of the verb is ak- (to flow). Because it is a single-syllable word ending in a consonant, it takes the -Ar form of the aorist suffix. According to vowel harmony, the 'a' in ak- gives us -ar. So, ak + ar makes akar (flows).

Why does the sentence use the aorist tense akar instead of the present continuous akıyor?

The aorist tense is used for general truths, scientific facts, and habits. By using akar, the sentence states a general fact about nature (water naturally flows under ice), rather than describing an action happening right at this exact moment.

Why is it buzun altında instead of just buz altında?

We are talking about specific ice (the ice), so Turkish uses a full possessive chain meaning "the ice's underneath". Buz (ice) takes the genitive suffix -un (of the), and alt (under/bottom) takes the possessive suffix -ı (its).

Where does the -n- come from in altında?