die Teilnahme
participation
Being present and taking part in an event, activity, or course.
Die Teilnahme am Gewinnspiel ist kostenlos.
Participation in the prize draw is free.

participation
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participation
Being present and taking part in an event, activity, or course.
Die Teilnahme am Gewinnspiel ist kostenlos.
Participation in the prize draw is free.

'Teilnahme' (participation) is a noun derived from the separable verb 'teilnehmen' (to participate). This verb literally means 'to take a part' and expresses that you are taking part in something.
Er hat seine Teilnahme am Marathon bestätigt.
He confirmed his participation in the marathon.
The noun 'Teilnahme' (participation) is almost always used with the preposition 'an' followed by the dative. You speak of 'Teilnahme an einer Konferenz' (participation in a conference) or 'am Wettbewerb' (in the competition).
Die Teilnahme an diesem Kurs ist für alle Mitarbeiter verpflichtend.
Participation in this course is mandatory for all employees.
In connection with registrations, 'Teilnahme' (participation) is often combined with verbs like 'bestätigen' (to confirm), 'zusagen' (to accept/confirm), or 'absagen' (to cancel).
Bitte bestätigen Sie Ihre Teilnahme bis spätestens Freitag.
Please confirm your participation by Friday at the latest.
visit / visitor
'Besuch' and 'Teilnahme' can both mean that someone is present at an event, a course, or an institution. 'Besuch' emphasizes more that you go there or are present, for example in 'Besuch eines Kurses' (attendance at a course), 'Besuch einer Schule' (attending a school), or visiting a website. 'Teilnahme' puts more emphasis on taking part or being officially involved. That is why 'Teilnahme' is especially appropriate for courses, competitions, meetings, or activities. They can be confused when it is only about being there. If taking part is important, 'Teilnahme' is more precise.

Für die Teilnahme am Wettbewerb muss man sich bis Freitag anmelden.
To participate in the competition, you have to register by Friday.
Der Besuch des Sprachkurses hilft mir beim Lernen.
Attending the language course helps me learn.