der Unterzeichner
signatory
A male person who signs a document, such as a contract, petition, or letter.
Alle Unterzeichner des Vertrags sind mit den Bedingungen einverstanden.
All signatories to the contract agree to the terms.

signatory
Loading your saved state.
signatory
A male person who signs a document, such as a contract, petition, or letter.
Alle Unterzeichner des Vertrags sind mit den Bedingungen einverstanden.
All signatories to the contract agree to the terms.

'Der Unterzeichner' (the signatory) is derived from the verb 'unterzeichnen' (to sign). The ending '-er' forms a noun for the male person who performs the action. 'Unterzeichnen' itself literally means to put one's writing ('Zeichen', sign/mark) 'under' a document.
Der Künstler unterzeichnete jedes seiner Werke.
The artist signed each of his works.
Very often, 'Unterzeichner' (signatory) is followed by a genitive that indicates which document was signed. Alternatively, a construction with 'von' + dative is used.
Die Unterzeichner des Briefes fordern sofortige Maßnahmen.
The signatories of the letter are demanding immediate action.
This word belongs to formal administrative and legal language. You typically find it in contracts, official letters, or reports about political agreements.
Der Notar las den Vertrag vor, bevor die Unterzeichner ihn signierten.
The notary read the contract aloud before the signatories signed it.
to sign
'unterzeichnen' and 'der Unterzeichner' belong to the same word family and both have to do with a signature. The difference is clear grammatically and in meaning: 'unterzeichnen' is the action, so it is a verb. 'Der Unterzeichner' is the male person who signs or has signed. The words can be confused because they look similar. Memory tip: A person signs a document; that person is the signatory.

Der Unterzeichner des Briefes bittet um eine schnelle Antwort.
The signatory of the letter asks for a quick response.
Vor dem Kurs müssen alle Teilnehmer das Formular unterzeichnen.
Before the course, all participants must sign the form.