Lesson 5: Natural Language Processing (NLP)

How computers understand, generate, and translate human language

What is NLP?

Natural Language Processing is a field of AI focused on enabling computers to read, understand, and produce human language. Modern NLP combines linguistics, machine learning, and large datasets to support tasks like translation, Q&A, and summarization.

Core Tasks

  • Text Classification: spam detection, topic labeling
  • Named Entity Recognition (NER): find names, places, dates
  • Sentiment Analysis: positive/negative/neutral feelings
  • Machine Translation: translate between languages
  • Question Answering / Chat: respond to user questions
  • Summarization: shorten text while keeping key info

Common Techniques

  • Tokenization & Normalization: split text, lowercasing, stemming/lemmatization
  • Feature Representations: Bag-of-Words, TF-IDF, word embeddings (Word2Vec, GloVe)
  • Neural Models: RNNs/LSTMs, CNNs for text
  • Transformers: attention-based models (BERT, GPT) for state-of-the-art performance

Modern NLP: Transformers

Transformers use a mechanism called self-attention to understand relationships between words, even when they’re far apart. Pretrained language models are fine-tuned for tasks like classification, QA, and summarization with relatively small labeled datasets.

Zero-shot & Few-shot

Large models can perform new tasks from instructions or just a few examples, reducing labeled-data needs.

Safety & Bias

NLP systems may reflect training data bias; evaluate outputs and apply safeguards.

Evaluation

Use proper metrics: accuracy/F1 for classification, BLEU/ROUGE for translation/summarization.

Simple NLP Workflow

  1. Collect text & clean it (remove noise, normalize)
  2. Choose representation (TF-IDF or embeddings)
  3. Train or fine-tune a model
  4. Evaluate on held-out data
  5. Deploy & monitor for drift/safety

Practical Uses

  • Customer support chatbots
  • Auto-tagging emails or documents
  • Summarizing meeting notes
  • Language learning assistance

Quick Quiz

1) Which task identifies names/places in text?

2) Transformers are powerful because they use…

3) A good text representation method before neural models is…

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