Русско-англо-русский юридический словарь

Alimony (also called aliment (Scotland), maintenance (England, Ireland, Northern Ireland, Wales, Canada), spousal support (U.S., Canada) and spouse maintenance (Australia)) is a legal obligation on a person to provide financial support to their spouse before or after marital separation or divorce. [...] Alimony is not child support, where, after divorce, one parent is required to contribute to the support of their children by paying money to the child's other parent or guardian. (Wikipedia)

In family law and public policy, child support (or child maintenance) is an ongoing, periodic payment made by a parent for the financial benefit of a child (or parent, caregiver, guardian, or state) following the end of a marriage or other relationship. (Wikipedia)

The key difference between alimony vs. child support is the intended use of each payment.

Alimony is paid for the benefit of a spouse; child support is paid for the benefit of any children resulting from the marriage.

Child support is designed to be used to meet the basics needs of the child. That includes things like food, clothing, medical care, housing, and other necessities. (The Balance)

The husband would be forced to pay his wife alimony for the rest of his life. (Cambridge English Corpus)

Alimony refers to the financial assistance and monetary support provided by one spouse to another after a marriage ends in divorce. Oftentimes, the receiving spouse must be unable to support themselves without the help of their ex-spouse. (US Law | Legal Information Institute)

There is no difference between spousal maintenance and alimony in the UK. Spousal maintenance is the legal term used in England and Wales, whilst alimony is a term, usually used in the USA, to reflect the same thing. (mediateuk.co.uk)