What is the crossword answer for the clue: Logical start?

BIO - a 3 letter word may be the answer you are looking for!

ECO - a 3 letter word may be the answer you are looking for!

GEO - a 3 letter word may be the answer you are looking for!

NEO - a 3 letter word may be the answer you are looking for!

IDEO - a 4 letter word may be the answer you are looking for!

THEO - a 4 letter word may be the answer you are looking for!

PATHO - a 5 letter word may be the answer you are looking for!

NEURO - a 5 letter word may be the answer you are looking for!

Logical start?

3 Character Answers:

BIO

ECO

GEO

NEO

4 Character Answers:

IDEO

THEO

5 Character Answers:

NEURO

PATHO