Learn Russian: Его речь течёт плавно и красиво. - His speech flows smoothly and beautifully.

The verb течь literally means 'to flow' or 'to stream' like water. Using it metaphorically for речь (speech) creates a vivid image of words coming out continuously, effortlessly, and without interruption. It highlights the graceful quality of his delivery rather than just the literal act of speaking.

We often see идти used with speech, such as in the phrase речь идёт о... Could we use идёт in this sentence instead?

No, they serve different metaphorical purposes. Речь идёт о... is a fixed idiom meaning 'the conversation is about' or 'the topic is'. If you want to describe the physical fluency and graceful delivery of the words themselves, you need the liquid movement metaphor of течёт (flows) or льётся (pours).

The translation uses 'smoothly'. Why use плавно instead of гладко here?

Both can mean 'smoothly', but they describe different things. Гладко refers to a physically smooth surface without bumps, often used metaphorically to mean 'without problems or hiccups'. Плавно describes movement that is gradual, continuous, and without sudden jerks. Since we are using a motion verb (течёт), the movement-focused плавно fits the water metaphor perfectly.

The infinitive is течь. Why does it conjugate with a 'к' in some forms but a 'ч' here?