What is an healthy relationship? what is an unhealthy relationship?

Here's my take...: Whether they are family members, friends, co-workers, or committed partners -- two people who enjoy doing things together and being together, without either making the other responsible for their own happiness. Teach rather than criticize; the relationship is more important than being right. Enjoy seeing the other person make their own decisions freely.

Many kinds: There are many kinds of relationships, and health might look different depending on the nature of the relationship. For instance, complete dependency of a small child upon s parent would be natural and healthy in a child-parent relationship, but unhealthy in adult-adult one. 2 adults need to agree on relationship ground rules; be trustworthy; genuinely care about each other, etc. See comment.

No easy answer: Cultural variability aside, and generally speaking, healthy relationships are based on trust, honesty, mutual respect, support, fairness, good communication, separate identities, and a sense of playfulness. Not all good relationships possess all of these characteristics at all times, but the absence of some of these factors has been associated with relational dissatisfaction, to varying degrees.