The spelling of the word "pactums" can be explained using IPA phonetic transcription. The /p/ sound is produced by plosive airflow in the vocal tract, followed by the vowel sound /æ/ which is pronounced with an open mouth and a low tongue position. The /k/ sound is produced with a plosive airflow in the back of the mouth, followed by the vowel sound /t/ which is produced by placing the tongue behind the teeth. The sound /ʌm/ is a nasal vowel sound with a 'm' sound at the end. Thus, the spelling of "pactums" is derived from the phonetic transcription of its sounds.