What does the prefix ortho mean?

The prefix "ortho" comes from the Greek word "ορθός" (orthos), which means straight, right, correct, or true. It's often used in scientific and technical contexts to indicate:

* A straight or perpendicular position: This is seen in words like orthogonal, which means perpendicular, and orthopedics, the branch of medicine dealing with bones and joints.

* A normal or standard position: For example, ortho-para hydrogen refers to the two different forms of hydrogen, with ortho being the more common and stable form.

* A specific chemical structure: In organic chemistry, ortho refers to a specific position of a substituent on a benzene ring.

So, the meaning of "ortho" depends on the context, but it generally implies a straight, correct, or standard position or arrangement.