A half bra is a brassiè in which one cup is missing, so that one breast is covered and the other is exposed. Two variants exist, one in which the left breast is exposed (KP88P2) and one in which the right breast is exposed (KP88P4).
Halfbras are sometimes also called halftops, but the very nature of the design tends to preclude other strapping configurations, such as a halfhalter or halfbandeau.
Halfbras offer a rich variety of combinations. In addition to covering just the right or left breasts, two halfbras can be simultaneously worn which together cover both, in this picture the green is worn over the yellow (KP88P3), although the yellow could also be worn over the green, an example of a layering dual. Of course the opposite of wearing both halfbras is to wear none (KP88I1), so that the complete matrix is a two by two grid.
Halfbras are obviously related to topless, with the primary difference being that with the halfbra only one breast is exposed and a garment is involved.
The natural sister species to halfbras is the maillot halftop, aka the single bare-breasted maillot (JD89E); these too can be combined with halfbras (C198410. RD8725, KP880303, JE9002), which brings one to the theme of layers.
Finally, halfbras are related to the handbra in two ways. First, certain combinations of hands may bare only a single breast and thus produce similar exposures, and secondly, hands may be combined with halfbras to modulate exposure.
A soutien-gorge which only half covers both breasts, often leaving the areola and nipple all or partly exposed, is called a demi-bra.
It is worth noting that halfbras are classified as a species of their own, and not a wild.