All Acts of Parliament (after 1963) are given a short title, year, and chapter number
e.g. Sex Discrimination Act 1975 (c. 65)
This means that the 'Sex discrimination Act' was the 65th Act to receive royal assent in 1975.
Acts of Parliament passed before 1963 are traditionally referred to by Regnal year and chapter number.
e.g. Highways Act 7 & 8 Eliz 2 (c.25)
This act was passed in the session of Parliament that covered the 7th and 8th years of Elizabeth II's reign.