perpendicular
Pronunciation: /ˌpəːp(ə)nˈdɪkjʊlə/
adjective
- 1at an angle of 90° to a given line, plane, or surface or to the ground: dormers and gables that extend perpendicular to the main roofline
- at an angle of 90° to the ground; vertical: the perpendicular cliff
- so steep as to be almost vertical: houses seem to cling by blind faith to the perpendicular hillside
- 2 (Perpendicular) denoting the latest stage of English Gothic church architecture, prevalent from the late 14th to mid 16th centuries and characterized by broad arches, elaborate fan vaulting, and large windows with vertical tracery: the handsome Perpendicular church of St Andrew the Perpendicular style
noun

Origin:
late Middle English (as an adverb meaning 'at right angles'): via Old French from Latin perpendicularis, from perpendiculum 'plumb line', from per- 'through' + pendere 'to hang'

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Remember that perpendicular ends with -ar.