Present tense verbs are normally conjugated by taking the stem of the verb then applying the appropriate ending to it depending on the subject of the sentence. However, there are some spelling rules to observe in certain situations.
The verb spreken (to speak), and some others like it, needs some additional adjustment.
Spreken consists of two syllables, an open syllable and a closed syllable (spre~ken). However in the singular forms the verb changes (Ik spreek. Jij spreekt). This is because the stem on its own is a single closed syllable. This means that the long vowel must double up, hence the “e” becomes “ee”.
The verb kennen (to know) consists of two closed syllables (ken~nen). Because the vowels are not doubled up they are short vowels. When the verb is reduced to its stem it becomes simply ken. In the singular persons the conjugations are ik ken, and jij/hij/zij kent.
Some verbs change the last consonant of the stem when the ending changes. The z and s interchange, and v and f interchange.
For example, the z in lezen (to read) becomes an s in the following forms: ik lees, and jij leest, but wij lezen stays the same as the infinitive.
Another example is that the v in schrijven (to write) becomes an f in the following forms: ik schrijf, and jij schrijft, but wij schrijven stays the sam