The Dutch verb stem and the four stem rules

The stem is the base form of a Dutch verb — what is left of the infinitive once you take off its ending. From werken (to work) you get the stem werk. Almost every tense is built on the stem, so getting it right is the first step in conjugation.

Take the infinitive, remove the -en ending, then adjust the spelling so the word still sounds the same. Dutch infinitives nearly always end in -en: kopen (to buy), wonen (to live), bakken (to bake).

Four rules turn the infinitive into a correct stem:

1. Drop -en. This gives the rough stem: werken → werk, kopen → kop..., bakken → bakk.... Rules 2–4 then fix the spelling.
2. Keep a long vowel long. A vowel written once in the infinitive (wo-nen, ko-pen) sits in an open syllable and is long there. In the stem it lands in a closed syllable, so you write it twice to keep the long sound: wonen → woon, kopen → koop, maken → maak. More on this in open and closed syllables.
3. A stem cannot finish with a doubled consonant, so one copy is dropped: bakken → bak, rennen → ren, zetten → zet.
4. A stem cannot end in v or z either. When it would, v switches to f and z to s: geven → geef, reizen → reis. See why v becomes f and z becomes s.

A handful of verbs end in -iën, such as skiën (to ski) and taxiën (to taxi, of a plane). These break the pattern above. The ik form keeps only the bare -i — ik ski, ik taxi — while the endings that add -t slip an -e- in first, so the -i is not misread: jij skiet, hij taxiet.

The stem is the building block for most forms of the verb:

• The ik form of the simple present: ik werk, ik woon.
• The jij and hij forms, which add -t to the stem: jij werkt, hij woont.
• The command form (imperative): Werk! (Work!), Ren! (Run!).
• The simple past and the past participle are also built from the stem.

The vowel-length rule is where most errors happen. Learners write won or kop by chopping off -en, forms that would be read with a short vowel (kop rhymes with English cop). The infinitive hides the length: because wo-nen and ko-pen split right after the vowel, a single o is already long there — but the stems woon and koop are each one closed syllable, so they need the double oo. Short-vowel verbs have no such trap: bakken keeps its short a as bak.