When speaking English, some parts of an utterance are given more emphasis than others through prominence. Prominence can occur at the syllable or sentence level and involves four aspects: pitch, quality, quantity, and stress. Pitch relates to vocal cord vibration and perceived high or low tones. Quality involves resonator shape and how distinct sounds are perceived. Quantity refers to sound length. Stress is caused by greater muscular energy and perceived as loudness. Accent is assigned based on a syllable's ability to initiate a pitch movement, whereas prominence can involve other factors without pitch variation. Words and compounds can have primary, secondary, or unaccented syllables. Accent placement helps distinguish meanings. Prominence is modified in connected speech through