The only only way to tell for sure whether someone is clinically depressed is to bring them to a doctor
who can interview them looking for key symptoms of depression. Depression is very common, but sometimes people can go through times in their life when they are sad, and this does not lead to depression. Unfortunately, sometimes it does.
Sometimes the difference between sadness and depression is time. If your husband just lost his job a few months ago, he is aloud to go through a grieving process that can look like depression. Grieving should not be treated with medication. However, if during this time, or afterward he develops disturbances in his sleep, disturbances in his appetite, pervasive feelings of guilt, or inability to enjoy activities that he used to enjoy, then depression may have set in.
I suggest that you schedule an appointment with your husband's primary care physician
. He is more likely to respond and open up to a doctor he already knows than someone he doesn't. His doctor can discuss his mood, appetite, sleeping pattern, and his ability to enjoy things he used to enjoy. If his doctor detects some depression, then he can get started on an antidepressant medication with plan for close followup. If his mood does not improve, then he may warrant referral to a psychiatrist