A verb that is composed of both a stem and a separable affix is known as a separable verb. The separable affix is usually a prefix or a suffix. In certain circumstances, a separable verb’s affix is capable of detaching from the stem and appearing in a separate part of the sentence. Separable verbs are one of the verb types frequently found in Germanic languages such as German and Dutch. They also appear in some non-Indo-European languages such as Hungarian.
One language known for its abundance of separable verbs is German. More often than not, in German, a separable verb will have a separable prefix, as in the an in anfangen, a verb that means “to begin,” or the zurück in zurückgehen, a verb that means “to go back.” Although many prefixes are separable in German, not all of them are. This fact can initially confuse some beginning language learners, because they sometimes have a tendency to separate verbs that are not actually separable.
Across the languages that employ separable verbs, the verb form is what generally dictates when the separable verb will separate. For example, in German, a separable verb will almost always separate except for when it is in its infinitive form, in its past participle with ge- inserted between the prefix and the stem or when it appears in a dependent clause. So, to say "Can we start now?" in German, one would use a modal requiring the infinitive, and thus the verb anfangen would not separate: "Können wir jetzt anfangen?" By contrast, to say "We start now" in German, the verb would separate to yield "Wir fangen jetzt an."
Although some linguists consider verbs to be true separable verbs only if their infinitive form is one word, many place a subset of English phrasal verbs in the separable verbs category. Examples of separable verbs in English are "to take out," as in, "Take out the trash" or "Take the trash out," and "to switch off," as in, "Switch off the light" or "Switch the light off." As these examples illustrate, unlike German separable verbs that consist of one word that is later broken apart, English separable verbs are phrasal verbs, or compound verbs consisting of more than one word. Phrasal verbs in English can consist of a verb and an adverb, a verb and a preposition or a verb with both a preposition and an adverb.
To have the possibility of being separable in English, a phrasal verb must be transitive. Transitive verbs take objects. A transitive phrasal verb can be either separable or inseparable, depending on the specific verb, but no intransitive verbs are separable. For example, the verb “to die down” cannot be separated because it is intransitive. The sentence “The party died down” would be correct, but "Died the party down" would be incorrect.
With separable English verbs, the speaker often can decide whether to separate the verb. For instance, both "The cops closed down the party" and "The cops closed the party down" would be correct. In such cases, there usually is not a strict formal rule, but native speakers will sometimes think that one choice “sounds better” than the other. Language learners often find that they get a feel for these nuances over time.