das Bedenken
concern
A feeling of doubt, worry, or uncertainty about something. Usually used in the plural.
Trotz einiger Bedenken stimmte er dem Plan zu.
Despite some concerns, he agreed to the plan.

concern / consideration
Loading your saved state.
concern
A feeling of doubt, worry, or uncertainty about something. Usually used in the plural.
Trotz einiger Bedenken stimmte er dem Plan zu.
Despite some concerns, he agreed to the plan.

'Das Bedenken' (concern / consideration) is a nominalized verb derived from the infinitive 'bedenken' (to consider). This process, in which a verb becomes a noun, is very common in German.
Das Bedenken aller Risiken ist Teil der Projektplanung.
Considering all risks is part of project planning.
In the meaning of 'Zweifel' (doubt) or 'Sorge' (worry), this word is almost always used in the plural. You speak of your 'Bedenken' (concerns).
Ich habe einige Bedenken bezüglich des neuen Projekts.
I have some concerns about the new project.
Common verbs used with 'Bedenken' (concerns, in the plural) are 'Bedenken haben' (to have concerns), 'Bedenken äußern' (to express concerns), or 'Bedenken zerstreuen' (to dispel concerns, meaning to take away worries).
Der Manager versuchte, die Bedenken seiner Mitarbeiter zu zerstreuen.
The manager tried to dispel his employees' concerns.
In the formal meaning of 'Überlegung' (consideration), 'Bedenken' is used in the singular. It often appears in the fixed expression 'nach reiflichem Bedenken' (after careful consideration), which means 'after thorough reflection'.
Nach reiflichem Bedenken hat sie das Jobangebot angenommen.
After careful consideration, she accepted the job offer.
doubt
'der Zweifel' and 'das Bedenken' both express that you are not completely sure. 'Zweifel' often refers to whether something is true, right, or possible. 'Bedenken' is usually used in the plural when you have worries or objections about a plan, decision, or action. That is why the words can be confused: both show uncertainty. But if you mean 'I am not sure that it is true', 'Zweifel' fits. If you mean 'I see problems with this plan', 'Bedenken' fits better.

Vor dem Umzug äußerten die Eltern mehrere Bedenken wegen der hohen Miete.
Before the move, the parents expressed several concerns about the high rent.
Nach der schlechten Erklärung hatte Tom Zweifel, ob die Lösung richtig war.
After the poor explanation, Tom had doubts about whether the solution was correct.