of, at, from or near the centre

main, principal; in the middle

situated or coming between in time, space, degree etc

middle, in-between

of middle size, quality etc; that by which something is expressed; a substance, surrounding, in which something exists or moves

midway, average

at the center; the point, position or part which is at an equal distance from two or more points etc or between the beginning and the end

central

in the middle (of a length, distance, speed etc)

middle

a standard of behaviour, appearance, speech etc expected or asked for; an average standard of achievement (e.g. in an exam)

average, standard

in agreement with what is usual, average or regular

common, usual

an average or normal amount, degree, value etc

average, equilibrium

middle, in-between

middle, in-between