Important - impotent

These two words can be confused by non-native speakers, at least in speech. To confuse them can be unfortunate.

• Important - pronounced with the stress on the second syllable, and with a stronger '-r-', 'im-POR-tent', IPA: /ɪm 'pɔː^r tənt/ - is an adjective used to describe things that matter. 'It is important for students to get enough sleep'; 'She has an important exam today', and 'His clothes are of no importance; it is his ideas that matter' are examples.
• Impotent - with the stress on the first syllable, and no trace of an '-r-', 'IM-pet-ent', IPA: /'ɪm pə tənt/ - means 'without power, or ability'. It is usually qualified with an adverb like 'politically', 'practically' or 'morally'. Its most common meaning nowadays in everyday speech is 'sexually impotent', where it refers to a male's lack of ability to perform.

As many men feel insulted if said to be impotent, it is, as was remarked above, unfortunate if the words important and impotent are confused. It would be unfortunate if you were to be heard saying that your (male) Professor was 'very impotent'!

The associated nouns are importance (IPA: /ɪm 'pɔː^r təns/) and impotence (IPA: /'ɪm pə təns/).