The phrase "be up to" is commonly used in English to indicate that someone is engaging in a particular activity or behaving in a certain way. The pronunciation of "be up to" is bi ʌp tu, with the stress on the second syllable of "up". The spelling of this phrase reflects the manner in which it is pronounced, with the word "to" clearly separated from the preceding words. Learners of English should note that the preposition "up" can be used in conjunction with many other verbs, including "come up", "bring up", and "stand up".