The connotations of the word spinster have changed over time so that it is now considered a derogotary term.
The Oxford English Dictionary says in its usage notes for the word: The development of the word spinster is a good example of the way in which a word acquires strong connotations to the extent that it can no longer be used in a neutral sense.
Previously both socially uncommon and unaccepted due to perceived roles, public awareness, modern socioeconomic factors and increasingly available popular and lengthier education and careers have made the single lifestyle a viable option for many Americans, especially after the Vietnam War.
Similar to the United States, single-person households are increasingly popular in the United Kingdom.
In legal definitions for interpersonal status, a single person is someone who is not in a relationship or is unmarried.