genügen
to suffice
To be present in a sufficient quantity or number; to be enough.
Für das Rezept genügt ein halber Liter Milch.
Half a liter of milk is enough for the recipe.

to suffice
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to suffice
To be present in a sufficient quantity or number; to be enough.
Für das Rezept genügt ein halber Liter Milch.
Half a liter of milk is enough for the recipe.

The verb 'genügen' (to suffice) is directly related to the adverb 'genug' (enough). Both express the idea of 'sufficient' or 'adequate'. If something genügt (suffices), you have enough of it.
Ich habe genug Geld dabei, das sollte für den Einkauf genügen.
I have enough money with me; that should suffice for the shopping.
When a person is mentioned for whom something is sufficient, that person is in the dative. The subject of the sentence is the thing that is sufficient.
Deine Erklärung genügt mir nicht.
Your explanation isn't enough for me.
'Genügen' is very often used in the impersonal form 'es genügt' (it is enough), often followed by a subordinate clause with 'wenn' (if/when) or an infinitive construction with 'zu' (to).
Es genügt, wenn Sie das Formular bis morgen abgeben.
It is enough if you submit the form by tomorrow.
In the meaning of 'Anforderungen erfüllen' (to meet requirements), the requirement that is being met is also in the dative. Typical phrases are 'den Ansprüchen genügen' (to meet the demands/expectations) or 'den Kriterien genügen' (to meet the criteria).
Sein Zeugnis genügte den Anforderungen der Universität.
His certificate met the university's requirements.
The reflexive form 'sich genügen' or 'sich selbst genügen' means that someone is content on their own and does not need company or outside help. The reflexive pronoun is in the dative here.
Er war ein Künstler, der sich und seiner Arbeit vollkommen genügte.
He was an artist who was completely sufficient unto himself and his work.
to hand / to suffice
'reichen' and 'genügen' can both mean that something is enough. In many everyday sentences, you can use both in a similar way. 'reichen' often sounds a bit more normal and everyday, especially with amounts, time, or money. 'genügen' sounds somewhat more formal and also fits well when something meets certain requirements. Learners may confuse the words because both express 'to be enough'. The important point is: 'reichen' is very common in everyday language, while 'genügen' often sounds more precise or official.

Für die Anmeldung genügt ein gültiger Ausweis.
A valid ID is sufficient for registration.
Für die Prüfung reichen mir zwei Stunden zum Wiederholen.
Two hours of review is enough for me for the exam.