In semiotics, the 'signifier' is the form that a sign takes, while the 'signified' is the concept it represents. This distinction, introduced by Ferdinand de Saussure, is fundamental to understanding how meaning is constructed and interpreted in language and communication.
Morphology is the branch of linguistics concerned with the structure and form of words in a language, including the study of morphemes, which are the smallest units of meaning. It explores how words are formed, how they relate to other words in the same language, and how they convey meaning.
Lexical substitution involves replacing a word in a text with another word that has a similar meaning, preserving the original context and intent. It is a challenging problem in natural language processing, requiring a deep understanding of semantics and context to ensure the coherence and readability of the text.