Which term best describes the quality of being smooth and connected in musical phrasing?

The term that best describes the quality of being smooth and connected in musical phrasing is legato. When a passage is played legato, each note is connected to the next without perceptible breaks or gaps, creating a flowing, seamless sound. This technique is often indicated in sheet music by a slur, which visually signifies that the notes should be performed in a smooth manner.

In contrast, marcato indicates a more pronounced and separated articulation, where notes are played with emphasis and a distinct attack. Hemiola refers to a rhythmic pattern that creates a feeling of shifting between two and three beats, which does not pertain to smoothness in phrasing. Lento describes a slow tempo and does not inherently relate to the connection between notes in the way legato does. Thus, legato is clearly the best choice for the quality of being smooth and connected in musical phrases.