The expression "chain of thought" can be replaced by several other terms, depending on the context and the desired level of formality. Some synonyms for this phrase include "train of thought," "stream of consciousness," "line of thinking," "thought sequence," and "mental progression." Each of these expressions implies a series of connected ideas or concepts that follow a logical order, whether consciously or unconsciously. While "chain of thought" is perhaps the most commonly used term, the use of synonyms can help to create more variety in writing and allow for a more nuanced expression of ideas.