al·ti·tude \'al-t&-"tüd also-"tyüd\ noun

1 a: the angular elevation of a celestial object above the horizon b: the vertical elevation of an object above a surface (as sea level or land) of a planet or natural satellite c (1) : a perpendicular line segment from a vertex of a geometric figure (as a triangle or a pyramid) to the opposite side or the opposite side extended or from a side or face to a parallel side or face or the side or face extended (2) : the length of an altitude 2: a high level (as of quality or feeling) <the altitudes of his joy> 3 a: vertical distance or extent b: position at a height c: an elevated region : EMINENCE -- usually used in plural. synonyms see HEIGHT

es·sen·tial \ i-'sen(t)-sh&l\ adjective

1: of, relating to, or constituting essence: INHERENT 2: of the utmost importance : BASIC, INDISPENSABLE, NECESSARY <essential foods> <an essential requirement for admission to college> 3: IDIOPATHIC <essential disease> <essential hypertension>. synonyms see FUNDAMENTAL, VITAL <means as important as to be indispensable>. FUNDAMENTAL applies to something that is a foundation without which an entire system or complex whole would collapse <fundamental principles of algebra>. VITAL suggests something that is necessary to a thing's continued existence or operation <cut off from vital supplies>.