orth - padd
- ortho rock
- orthocompound
- orthodox economy
- orthodox method of manufacture
- orthodox process
- orthodox school
- orthogoanl polynomial
- orthogonal
- orthogonal array
- orthogonal design
- orthogonal experiment
- orthogonal field
- orthogonal matrix
- orthogonal polynomial
- orthogonal transformation
- orthogonal vector
- orthogonality
- orthogonality relation
- orthography
- orthonormal vector
