pˌiːˌaɪkˈeɪz ɐkɹˈuː ˈɪntɹɛst pˈiəɹɪəd ˈæftɚ pˈiəɹɪəd, ðˈʌs ɪŋkɹˈiːsɪŋ ðɪ ˌʌndɚlˈaɪɪŋ pɹˈɪnsɪpəl ˈaɪ.ˈiː., kˈɑːmpaʊnd ˈɪntɹɛst.
PIKs accrue interest period after period, thus increasing the underlying principal (i.e., compound interest).