parity

Concise Oxford English Dictionary © 2008 Oxford University Press:
parity1 /ˈparɪti/

▶noun

• 1 equality or equivalence, especially as regards status, pay, or value.

• 2 Mathematics the fact of being an even or an odd number.

• 3 Physics the property of a spatial wave equation that either remains the same or changes sign under a given transformation.

– origin C16: from late L. paritas, from par ‘equal’.

Concise Oxford English Dictionary © 2008 Oxford University Press:
parity2 /ˈparɪti/

▶noun Medicine the fact or condition of having borne a specified number of children.

– origin C19: from parous ‘having borne offspring’ (back-form. from adjs. ending in -parous) + -ity.