For example; 

Half-sibling and step-sibling are two different types of sibling relationships:

Half-Sibling

A half-sibling is the child of one biological parent and a different parent. Half-siblings share one biological parent but not both (either the same mother or father).

Step-Sibling

A step-sibling is the child of one's parent's spouse from a previous marriage or relationship. Step-siblings do not share any biological parents.

For more clarification:

If your biological father married 2 or more wives, the children from the other wives are your half-siblings, because you all have the same biological father.

If your father married another woman who already had a child somewhere else, the child is your step-sibling, because you both don't have the same biological father or mother.

Do you have any question on this?

Let me know in the comments.

What other similar English words with different meanings do you know?