Amna Navaz, the word is:
in·te·gral........(Not in(TEG) ral, as you pronounced it tonight)
/ˈin(t)əɡrəl,inˈteɡrəl/
adjective
1.
necessary to make a whole complete; essential or fundamental.
"games are an integral part of the school's curriculum"
Similar:
essential
fundamental
basic
intrinsic
inherent
constitutive
innate
structural
vital
indispensable
necessary
requisite
Opposite:
incidental
peripheral
2.
MATHEMATICS
of or denoted by an integer.
nounMATHEMATICS
/ˈin(t)əɡrəl/
a function of which a given function is the derivative, i.e. which yields that function when differentiated, and which may express the area under the curve of a graph of the function.