The word has two possible plurals — formulae and formulas. The “ae” in the final syllable of “formulae” is pronounced like the “ee” in “bees”, “fees”, and “knees”. The stress in the case of all three words is on the first syllable. The Latin plural “formulae” is the preferred word in scientific contexts, while “formulas” is used elsewhere. For example, one talks about “mathematical formulae” and “political and diplomatic formulas”.
The Hindu- ‘Know Your English’ Series, Jan 03, 2005
Check out my new initiative for English Lovers- www.exploreabc.com
Join Our New Facebook Club- www.facebook.com/exploreabc
KYE 