Adult contemporary music, frequently abbreviated AC, is a type of radio format that plays mainstream contemporary popular music, excluding hip hop, hard rock, some teen pop music, and rhythmic dance tracks (though during the 2000s, these have been included), which is intended for a mature adult audience. Radio stations playing this format will often target 25-54 year-olds, the group most valued by advertisers. AC is generally divided into 4 groups; "Hot AC," also known as "Adult Top 40," "Soft AC," also known as "Lite," "Urban AC," also known as "Urban Contemporary," and "Religious AC." Some radio stations play only Hot AC; some play only Soft AC, and some play both. Thus it is not usually considered a specific genre of music, since it is merely an assembly of selected tracks of musicians of many different genres.