What is a one-word synonym for "science lover"?

Solution 1:

The archaic answer is a philosopher, which comes from the word philosophy, where

• philo = love; and
• sophia = knowledge, wisdom:

philosophy (n.) c. 1300, "knowledge, body of knowledge," from Old French filosofie "philosophy, knowledge" (12c., Modern French philosophie) and directly from Latin philosophia and from Greek philosophia "love of knowledge, pursuit of wisdom; systematic investigation," from philo- "loving" (see philo-) + sophia "knowledge, wisdom," from sophis "wise, learned;" of unknown origin. - Online Etymology Dictionary

Support for the link between philosophy and science comes from the term natural philosophy:

natural philosophy noun [mass noun] archaic Natural science, especially physical science. - ODO

Note that calling a lover of science a philosopher would now be somewhat misleading. The modern understanding has specialised this usage to an academic context, hence the Ph in the title, Ph.D.

(This answer is an expanded version of a popular comment I made to a very similar question. I'm including it here for historical interest in the term philosopher.)

Solution 2:

Maybe a science geek?

geek [USUALLY WITH MODIFIER] A knowledgeable and obsessive enthusiast:

a computer geek

It captures your knowledge without pointing to a classic education and your enthusiasm for the topic.

Solution 3:

Boffin is a good one. Probably most recognised in the UK, it is slang for a scientist, engineer, or other person engaged in technical or scientific work. Originally, the word was armed-forces slang for a technician or research scientist but now the word can be used for anyone with specialist technical knowledge whether it is applied professionally or on an amateur basis.

To my ears it is usually a positive word but like geek or nerd it can have slightly negative connotations of someone who is clever but socially awkward.