“i do not need to use a citation if i paraphrase because i put it in my own words.”
why is this statement inappropriate?

The statement is inappropriate because although you've paraphrased the materials that you've obtained from a source, the idea is still not yours and this violates the right of the author to be recognized for his works. A proper citation should still be used even if paraphrasing is done.

Photo means light and synthesis means combination so combination of light