I UK [ˈfɔː(r)mə(r)] / US [ˈfɔrmər] adjective, pronoun ***

Former can be used in the following ways: - as an adjective (only before a noun): She still visits her former husband. - as a pronoun (after "the"): Given the choice between rose pink and olive green, I'd choose the former every time.
1) used for describing someone or something that had a particular job, title, status etc in the past, but not now

The ceremony honoured all the former presidents who are still living.

the former Soviet Union

He abandoned his former career as a geologist.

2) formal used for referring to times in the past

Marble pillars and high painted ceilings remain from former times.

3) formal used for referring to the first of two people or things that you have mentioned. Use the latter to refer to the second person or thing

Both Williams and Andrews claim the property. The former insists that it was a gift.

be a shadow/ghost of your former self — to be much less healthy or successful, or to be in much worse condition than before

He returned from the war a shadow of his former self.

II UK [ˈfɔː(r)mə(r)] / US [ˈfɔrmər] noun

first/second/third etc formerBritish

old-fashioned a student in the first/second/third etc year of secondary school

English dictionary. 2014.