Sentiment Analysis

Sentiment Analysis extracts the subjective dimension of text — the opinions, emotions, and attitudes expressed by the author. At its simplest, it classifies text as positive, negative, or neutral. More sophisticated approaches perform fine-grained sentiment analysis (identifying degree of sentiment on a scale), aspect-based sentiment analysis (determining sentiment toward specific product features or entities), and emotion detection (recognizing joy, anger, sadness, surprise).

The technology has evolved from lexicon-based approaches (counting positive and negative words from predefined dictionaries) to machine learning classifiers (Naive Bayes, SVMs on TF-IDF features) to the current state of the art: Transformer-based models fine-tuned on annotated sentiment datasets. BERT and its variants now achieve near-human performance on standard benchmarks, capturing subtle contextual cues — sarcasm, negation, domain-specific sentiment — that earlier methods missed.

One of the core challenges is domain adaptation: sentiment in product reviews is very different from sentiment in financial news, medical notes, or political discourse. A model trained on movie reviews may perform poorly on restaurant reviews, let alone earnings call transcripts. Domain-specific fine-tuning and aspect extraction are standard solutions. Multilingual sentiment analysis adds another layer of complexity — sentiment expressions are highly language- and culture-specific.