In terms of true medical terms yes, but the terms tend to get used generally more for depression being people who just feel low all the time, and bi-polar being people who "swing both ways" as it were.
Its a strange situation cause the medical profession seems to have lumped them together more recently and then seperated them again by calling them bilpolar and bipolar-2 IIRC
Bipolar is basically what traditionally gets called depression, as it only goes in one direction (ie downwards!), bipolar 2 is the one that goes both ways and is what normally gets called bipolar, even a lot of GP's will confuse the terms.

Another very closely related (but worse!) condition is schizophrenia, which basically has similar symptoms but then some others as well (delusions, voices, etc).