Yes, there is. You double the consonant if you have the combination CVC (consonant/vowel/consonant) as the last three letters of the present tense of the verb. This applies to single-syllable words (such as 'tip') and to polysyllabic words where the last syllable bears the stress ( such as 'refer'). sit - sitting swim - swimming hug - hugging hit - hitting run - running and refer - referring permit - permitting Compare 'hit' with 'heat', for example. 'Hit' has the CVC sequence, so you double the consonant - hitting - whereas 'heat' has the sequence VVC, so you don't double it - heating. Or compare the two words 'hoping' and 'hopping'. 'Hoping' comes from the verb 'hope' - you take off the 'e' and add -ing. This word has a long 'o' sound. 'Hopping' comes from the verb 'hop' (meaning to do a little jump). 'Hop' has the sequence CVC, so you double the consonant to make 'hopping'. This word has a short 'o' sound. As you can see, it's all about long and short vowel sounds. Basically, the short vowel sounds need a doubled consonant and the long ones don't. NB One grey area is polysyllabic verbs ending in 'l' which are spelt with a single 'l' in US English (traveling), but a double 'l' in British English (travelling) even though the last syllable isn't stressed. That's the only exception to the rule.

Yes, there is. Based on your examples, what do you think the rule is? :) if you're not sure, look at the verbs which don't take a double consonant. What is the difference?

yes and the rule is so simple: * to add a suffix to a one-syllable word with a single vowel followed by a single consonant, double the final consonant. ex: run + -ing = running sad+ -eat = saddest fat + -er = fatter cut + -able = cuttable. hope I could make it clear cut for you. :)