adjective

• Well grounded or justifiable, pertinent.
• Acceptable, proper or correct; in accordance with the rules.
• Related to the current topic, or presented within context, relevant.
• (logic) Of a formula or system: such that it evaluates to true regardless of the input values.
• (logic) Of an argument: whose conclusion is always true whenever its premises are true.
• (Christianity, theology) Genuine - as distinguished from efficient or regular - sacrament.