der Konkurrent
competitor
A person, company, or group that is in competition with others to achieve the same goal.
Apple und Samsung sind große Konkurrenten auf dem Smartphone-Markt.
Apple and Samsung are major competitors in the smartphone market.

competitor
Loading your saved state.
competitor
A person, company, or group that is in competition with others to achieve the same goal.
Apple und Samsung sind große Konkurrenten auf dem Smartphone-Markt.
Apple and Samsung are major competitors in the smartphone market.

'Der Konkurrent' (the competitor) belongs to a word family. The related noun is 'die Konkurrenz' (the competition), and the verb is 'konkurrieren' (to compete).
Die beiden Firmen konkurrieren um die besten Mitarbeiter.
The two companies are competing for the best employees.
'Konkurrent' (competitor) is a noun of the N-declension. This means it takes the ending '-en' in all cases except the nominative singular. This also applies to the entire plural.
Er sprach mit seinem größten Konkurrenten.
He spoke with his biggest competitor.
Common adjectives are 'ein starker Konkurrent' (a strong competitor), 'der größte Konkurrent' (the biggest competitor), or 'der direkte Konkurrent' (the direct competitor). You can also say that a company is a 'Konkurrent auf dem Markt' (competitor in the market).
Unsere Firma hat einen neuen, starken Konkurrenten bekommen.
Our company has gained a new, strong competitor.
participant
'der Teilnehmer' and 'der Konkurrent' can both describe people in a competition. 'Teilnehmer' only says that someone is taking part. 'Konkurrent' additionally says that someone is competing against others for the same goal, for example for a prize, customers, or a victory. The words can be confused because in a competition, many participants are also competitors at the same time. If participation is the main focus, 'Teilnehmer' fits. If the competition against others is important, 'Konkurrent' is more precise.

Im Finale ist Max ein starker Konkurrent für die anderen Läufer.
In the final, Max is a strong competitor for the other runners.
Jeder Teilnehmer bekommt vor dem Lauf eine Startnummer.
Each participant receives a race number before the run.