The spelling of the word "reglaecus" can be explained through its phonetic transcription in IPA. The transcription is [ˈrɛɡlækəs], which shows that the word begins with the sound /r/ followed by the short vowel /ɛ/ and the consonant cluster /gl/. The second syllable contains the short vowel /æ/ and the consonant /k/. The final syllable consists of the unstressed vowel /ə/ and the consonant /s/. The correct spelling of the word is important to ensure clarity in communication and avoid confusion.