Inflammation is the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. It is a protective attempt by the organism to remove the injurious stimuli as well as initiate the healing process for the tissue.
Inflammation is not a synonym for infection. Even in cases where inflammation is caused by infection it is incorrect to use the terms as synonyms: infection is caused by an exogenous pathogen, while inflammation is the response of the organism to the pathogen.
Inflammable subsances means Substances which catch fire very quickly viz. petrol, kerosene, spirit etc. Watch the tanker carrying petrol in your city and you will find the Word Highly inflammable. Same in case of rail containers carrying petroleum products.