German prefix verbs: separable and inseparable

German prefix verbs are verbs whose meaning is changed or refined by attaching a prefix to a base verb. They fall into three categories: always-separable (an open, growing list — anrufen, aufstehen, mitkommen, einkaufen), always-inseparable (a closed set of 7 prefixes: be-, ge-, er-, ver-, zer-, ent-, emp-), and dual-mode (6 prefixes — durch-, über-, um-, unter-, wider-, wieder- — that can go either way depending on stress and meaning). Knowing which bucket a verb falls into tells you everything about how it behaves in sentences, in Perfekt, and with zu + Infinitiv.

The 7 always-inseparable prefixes are: be-, ge-, er-, ver-, zer-, ent-, and emp- (a phonetic variant of ent- before /f/). This list is closed — there are no exceptions and no new additions. Verbs with these prefixes never separate in any tense, never add ge- in the Partizip II, and their prefix is always unstressed. Examples: besuchen (visit), gefallen (like), erreichen (reach), verstehen (understand), zerbrechen (break apart), entdecken (discover), empfehlen (recommend).

The stress test is the definitive rule: stress on the prefix = separable (ánrufen, áufstehen); stress on the verb root = inseparable (besúchen, verstéhen). This single test covers always-separable and always-inseparable prefixes with no exceptions. For the 6 dual-mode prefixes (durch-, über-, um-, unter-, wider-, wieder-), the stress test is both the diagnostic and the rule — same prefix, stress shift, different meaning: úmfahren (separable: run over) vs umfáhren (inseparable: drive around).

Separable verbs insert ge- between prefix and stem: anrufen → angerufen, aufstehen → aufgestanden, einkaufen → eingekauft. Inseparable verbs add no ge- at all: besuchen → besucht, verstehen → verstanden, entdecken → entdeckt. The rule mirrors the stress test: if the prefix is stressed (separable), ge- goes inside; if the prefix is unstressed (inseparable), no ge- is added anywhere.

In a main clause, the separable prefix flies to the end of the clause (Satzklammer): "Ich rufe dich um sechs Uhr an." In subordinate clauses introduced by a conjunction (weil, dass, wenn…), the verb and prefix reunite at the end: "…weil ich dich anrufe." In Perfekt, the prefix + ge- + stem form one word in Partizip II position: "Ich habe dich angerufen." With a modal verb, the full infinitive is written as one word at the end: "Ich muss dich anrufen."

Six prefixes — durch-, über-, um-, unter-, wider-, wieder- — behave as separable or inseparable depending on stress and meaning. The stress test is definitive: stressed prefix = separable (literal/concrete meaning); unstressed prefix = inseparable (figurative/abstract meaning). Three high-frequency pairs: úbersetzen (separable: ferry across) vs übersétzen (inseparable: translate); úmfahren (separable: knock over / run down) vs umfáhren (inseparable: drive around); wíederholen (separable: fetch back) vs wiederhólen (inseparable: repeat).

With separable verbs, zu inserts between the prefix and the stem — written as one word: aufzustehen, anzurufen, einzukaufen. This mirrors the Partizip II ge- insertion: the prefix stays attached, the particle (zu or ge-) slots in the middle. Three examples: "Ich versuche, früh aufzustehen"; "Er hat vergessen, mich anzurufen"; "Sie plant, morgen einzukaufen." For inseparable verbs, zu attaches normally to the front of the verb: zu besuchen, zu verstehen.

emp- is a phonetic alternation of ent- that appears before the consonant /f/ in exactly three modern German verbs: empfehlen (recommend), empfangen (receive), empfinden (feel/perceive). Every other ent- verb keeps the standard spelling (entdecken, entfernen, entstehen). The /t/ assimilates to /p/ before /f/ for ease of articulation — emp- and ent- are the same prefix etymologically. There are no other emp- verbs in modern standard German.