Rational (adjective)

1. Having reason or understanding; using reason.
2. Based on reason or logic.
3. Having a coherent, logical, and plausible structure or explanation.

Origin:

From latin rationalis ("of reason"), from ratio ("reason, calculation").

Examples:

1. It is rational to assume that there is a connection between the two events.
2. The decision was made for rational reasons.
3. The explanation was rational and clear.
4. The proposal was rational and well-thought-out.
5. The argument was rational and convincing.