A synonym for valid could be credible or legal.
coincide, concur, conform, correspond
A synonym is a word that means the same, or almost the same. So yes the word absurd could be a synonym form another word or there are synonyms for the word absurd.
A synonym for regularly is common!
A synonym to order is decree
Concur means to agree. "I concur with the findings of the report."
concur, conduce, connect
A synonym for valid could be credible or legal.
concur Agree, consent, accede, assent, concur
You make a valiant point, and because of that, I concur.
Scientists concur with the opinion that the Sun is the center of our solar system. Concur is a verb which means to agree.
"I concur."
The opposite of agreeing is disagreeing.
agree
The word 'concur' is a verb, meaning to have the same opinion, to agree; occurring at the same time, to coincide. Example sentences: Her mother would not concur with that action. Oh dear, the date of the graduation and the wedding concur. The council could not concur on a response to the problem. Since we all concur, the company picnic will be scheduled for the last Friday of July. Some concur with the findings, some do not.
That is the correct spelling of "concur" but whence is an archaic adverb or conjunction. The modern use of concur is with the prepositions such as in, on, or with. The word "when" might be used in an unrelated context (As for the decision, the judges were expected to concur when they meet later this week).
synonymize