Complex sentence: In terms of sounds, Czech possesses a glottal stop before initial vowels, Slovak uses long vowels less frequently, and Slovak possesses long forms of the consonants "r" and "l" for when they function as vowels.
Split into simpler sentences: In terms of phonetic differences, Czech is characterized by having a glottal stop before initial vowels, and Slovak by using long vowels less frequently than Czech. Slovak also has long forms of the consonants "r" and "l" for when they function as vowels.