Words such as "lady", "grandad" and "youth" are best avoided in the workplace because they can cause offence, according to the TUC.
The union umbrella group has set out its concerns in a document called Diversity in Action that advises trade unionists on the "appropriate use of language" about race, sex and age.
On age, it says: "Being old in British society carries connotations of being worn out and of little further use."
The guide says "grandad" and "grandma" may offend some people, as well as "old fool" and "old codger".
It goes on: "Equally, 'youth' has connotations of inexperience, impetuosity, and unreliability or even dishonesty." "Young people" is preferable, it says.
In the section on sex and language, the guide says: "The term 'lady' is not universally accepted and should not generally be used.
"The terms 'love', 'dear' and 'pet' may offend some people, especially women, and should not be used."
The TUC says that most people want to avoid causing offence and the guide will show when care is needed.
"We do not seek to achieve political correctness; we do want to achieve professional appropriateness."