Constitutional means to do with the basic laws of a state. A constitutional crisis, constitutional reform, unconstitutional.
In countries with a written constitution, a court can strike down a law as unconstitutional; Britain has no such document and no such power, which is why constitutional crisis there means a dispute about convention rather than about text. As a noun, a constitutional is an old-fashioned word for a walk taken for health. Note constitution, both the document and the body's make-up; and constitutionally, which can mean either by law or by nature.
1adjectiveconstitutionalTo do with the basic laws of a state.
“Changing the voting age would require a constitutional amendment.”
2nounwalkA walk taken for health.
“Every morning after breakfast, the old colonel went out for his constitutional.”
constitutional is a quality relating to founding law.
Latin constituere means to set up — con- plus statuere, to establish, from stare, to stand. A constitution is what a state stands on, and constitutional questions are about the foundations.
Proto-Indo-European
*steh₂- — to stand (up)
Latin
cōnstitūtiō
Old French
constitucion
Middle English
constitucioun
English, today
constitutional
Built from
From constitution + -al. Constitution is derived from Middle English constitucioun, constitucion (“edict, law, ordinance, regulation, rule, statute; body of laws or rules, or customs; body of fundamental principles; principle or rule (of science); creation”) from Old French constitucion (modern French constitution), a learned borrowing from Latin cōnstitūtiō, cōnstitūtiōnem (“character, constitution, disposition, nature; definition; point in dispute; order, regulation; arrangement, system”), from cōnstituō (“to establish, set up; to confirm; to decide, resolve”) (from con- + statuō (“to set up, station; to establish; to determine, fix”) (ultimately from Proto-Indo-European steh₂- (“to stand (up)”))) + -tiō, -tiōnem.
Etymology from Wiktionary, CC BY-SA