Linguistic Levels: Morphology, Syntax (POS, parsing), Semantics, Pragmatics, Discourse
Representation: Tokens, subwords (BPE/WordPiece/SentencePiece), characters
Classical Methods: Bag-of-words, n-grams, TF-IDF
Embeddings: word2vec, GloVe, fastText, contextual embeddings (ELMo, BERT-style)
Text Cleaning: lowercasing, normalization, stopword removal, stemming/lemmatization, de-duplication