✔ 最佳答案
Strictly speaking, a single person is an unmarried person, and is therefore available to be pursued to enter into a relationship that would lead to marriage.
Likewise, a married person, by law and by custom (except certain religion and culture) is expected to be committed to the spouse and is therefore not available to enter into another relationship with a third person.
Therefore, in that sense "single" and "available" would mean the same thing.
However, nowadays, a legally single person can have a close relationship with another peron, usually known as boyfiend/girlfriend, partner, fiancee, common-law husband/wife, lover, etc. It then becomes questionable whether this person is "available" or not.
By the same token, a legally married person may declare himself/herself available to more relationships, especially with the consent or silence of the legal partner.
Also, sometimes a single person may choose not to be available, for various reasons, including lack of interest, lack of trust, fear of betrayal, or religious (e.g. a Catholic priest or nun, a Buddist monk or nun).
Consequently, "single" and "available" do not necessarily mean the same thing. A single person may not be available, and an available person may not be single.
In the dating circle, the more popular term frequently used is whether a person is "attached" or "unattached". Usually an unattached person is single, separated, widowed, or divorced, and is not having a steady relationship. This unattached person is therefore "available" to start a new relationship.
If, however, one is looking for a single person who is truly available for a relationship leading to marriage, unfortnately this may require precise specification, such as "single, unattached, and available (for marriage)"