What are common techniques used in NLP?

Common techniques in natural language processing (NLP) focus on processing text data, extracting meaningful patterns, and building models to understand or generate language. These techniques typically fall into three categories: text preprocessing, feature extraction, and machine learning models. Each step addresses specific challenges, such as handling unstructured text, converting words into numerical representations, and training algorithms to perform tasks like classification or translation.

Text preprocessing is the first step, where raw text is cleaned and standardized. Tokenization splits text into smaller units like words or subwords (e.g., using libraries like NLTK or spaCy). Stop word removal filters out common but uninformative words (e.g., “the,” “and”) to reduce noise. Stemming and lemmatization simplify words to their root forms (e.g., “running” → “run”), though lemmatization uses grammar rules for more accuracy. For example, spaCy’s lemmatizer converts “better” to “good.” These steps ensure consistency and reduce complexity for downstream tasks. Handling case sensitivity (lowercasing) and special characters (like punctuation) is also common, especially for tasks like sentiment analysis or topic modeling.

Feature extraction converts text into numerical formats that algorithms can process. Bag-of-words (BoW) represents text as word frequency counts, while TF-IDF (Term Frequency-Inverse Document Frequency) weights words by their importance across documents. Word embeddings like Word2Vec or GloVe map words to dense vectors, capturing semantic relationships (e.g., “king” – “man” + “woman” ≈ “queen”). Modern approaches like BERT generate context-aware embeddings by analyzing surrounding words. For instance, the word “bank” in “river bank” vs. “bank account” gets different vector representations. Libraries like scikit-learn provide tools for BoW and TF-IDF, while frameworks like Hugging Face’s Transformers offer pretrained embedding models.

Machine learning models use these features to solve NLP tasks. Traditional models like Naive Bayes or Support Vector Machines (SVMs) work well with TF-IDF features for classification (e.g., spam detection). Neural networks, such as Recurrent Neural Networks (RNNs) or Transformers, handle sequential data and long-range dependencies. For example, LSTMs (a type of RNN) process text sequentially, making them useful for text generation. Transformers, with self-attention mechanisms, excel at tasks like translation (e.g., Google’s BERT or OpenAI’s GPT). Transfer learning allows developers to fine-tune pretrained models (like BERT) on specific datasets, reducing training time. Tools like PyTorch or TensorFlow enable custom model building, while APIs like Hugging Face’s pipeline simplify deployment for tasks like summarization or named entity recognition.