Introduction to Natural Language Processing (NLP)

Afzal Badshah, PhD
6 min readMay 17, 2024

Natural Language Processing (NLP) is a subfield of artificial intelligence (AI) that focuses on the interaction between computers and humans through natural language. The ultimate goal of NLP is to enable computers to understand, interpret, and generate human language in a way that is both meaningful and useful. Detailed tutorial on Data Science can be visited here.

Key areas of NLP

Text Analysis: Text analysis involves understanding and processing textual data to extract meaningful information. For example, in social media monitoring, companies use sentiment analysis to gauge public opinion about their products by analyzing customer reviews and social media posts. A brand might track tweets mentioning their product to determine if the overall sentiment is positive, negative, or neutral, helping them adjust their marketing strategies accordingly.

Machine Translation: Machine translation refers to the automatic translation of text or speech from one language to another. An example is Google Translate, which travellers use to communicate in foreign countries. People use it in a daily bases, like Google translator to translate their text from one language to other. For example, it can convert your native language to Urdu or Hindi etc.

Speech Recognition: Speech recognition converts spoken language into text, enabling hands-free interaction with devices. Virtual assistants like Siri and Alexa are prime examples, where users give voice commands to perform tasks. For instance, someone can ask Alexa to play music, set a timer, or provide the weather forecast without touching their device, enhancing convenience and accessibility.

Text Generation: Text generation involves creating new text based on a given input. A common use case is chatbots for customer service, which handle customer inquiries on websites. For example, a chatbot can provide information about order status or return policies, offering instant support to customers and reducing the need for human intervention.

Named Entity Recognition (NER): Named Entity Recognition (NER) identifies and classifies key elements in text, such as names, organizations, and locations. Financial institutions use NER to automate form processing, extracting information from loan applications like names, dates, amounts, and addresses. This speeds up processing time and reduces manual data entry errors, improving efficiency.

Part-of-Speech Tagging (POS): Part-of-Speech Tagging (POS) assigns parts of speech to each word in a sentence. Grammar-checking tools like Grammarly use POS tagging to provide suggestions for improving grammar and style. For instance, it can identify incorrect verb usage or suggest changes to enhance sentence structure in a user’s writing, making their text more polished and professional.

Dependency Parsing: Dependency parsing analyzes the grammatical structure of a sentence to understand the relationships between words. This is essential for voice-activated navigation systems, which need to comprehend complex spoken instructions. A navigation app can interpret commands like “Find the nearest gas station and route me there avoiding highways” by understanding the relationships between words and actions and providing accurate and useful directions.

The workflow of NLP

In this section, we look at the main steps or stages in the NLP workflow

Data Collection: Suppose you want to create an NLP model to analyze movie reviews. The first step is to collect a dataset of movie reviews from sources like IMDb or Rotten Tomatoes. This dataset will include text reviews along with ratings (e.g., positive or negative).

Data Preprocessing: Once you have the reviews, you need to clean the text. This involves removing punctuation, converting text to lowercase, removing stop words (common words like “the”, “is”, “and”), and stemming or lemmatizing words (reducing words to their base or root form). For instance, the review “The movie was fantastic!” would be preprocessed to “movie fantastic”.

Tokenization: Tokenization is the process of breaking down text into individual words or tokens. For the review “movie fantastic”, tokenization would result in two tokens: [“movie”, “fantastic”].

Feature Extraction: Convert the tokens into numerical features that a machine-learning model can understand. One common method is Bag of Words (BoW), where each word in the vocabulary is represented as a feature. For instance, if your vocabulary includes “movie”, “fantastic”, “boring”, then the review “movie fantastic” might be represented as a vector [1, 1, 0] (1 for “movie”, 1 for “fantastic”, 0 for “boring”).

Model Training: Use the numerical features to train a machine learning model. Suppose you use a classifier like logistic regression or a more complex neural network. You feed the model the feature vectors and their corresponding labels (positive or negative). The model learns the patterns associated with each sentiment.

Model Evaluation: After training, you evaluate the model’s performance using a separate set of reviews not seen during training (test set). Common evaluation metrics include accuracy, precision, recall, and F1 score. If your model correctly classifies 90 out of 100 reviews as positive or negative, it has an accuracy of 90%.

Prediction: With the trained and evaluated model, you can now predict the sentiment of new, unseen reviews. For instance, given a new review “The movie was boring”, the model might predict a negative sentiment based on the patterns it learned during training.

NLP Tools and Libraries

To work effectively in NLP, various tools and libraries have been developed, each offering unique capabilities and functionalities. Here are some of the most widely used NLP tools and libraries, along with their key features and typical use cases.

NLTK (Natural Language Toolkit): A comprehensive library for working with human language data in Python. It provides easy-to-use interfaces along with a suite of text-processing libraries for classification, tokenization, stemming, tagging, parsing, and semantic reasoning.

Use Case: Educational purposes and initial prototyping of NLP projects.

Example: Tokenizing a sentence into words, performing sentiment analysis, or parsing sentences.

spaCy: An industrial-strength NLP library designed for production use. It’s fast and efficient, offering pre-trained models for various languages. It includes features like tokenization, part-of-speech tagging, named entity recognition, and dependency parsing.

Use Case: Building large-scale NLP systems and applications.

Example: Extracting entities from text or performing complex linguistic annotations on large text corpora.

Stanford NLP: A suite of NLP tools provided by Stanford University, offering functionalities such as part-of-speech tagging, named entity recognition, parsing, and coreference resolution.

Use Case: Research and development in NLP, especially in academic settings.

Example: Analyzing grammatical structure and extracting syntactic relationships in sentences.

Transformers (by Hugging Face: A library that provides thousands of pre-trained models in over 100 languages for tasks like text classification, information extraction, question answering, and text generation. It supports models like BERT, GPT-3, and T5.

Use Case: Implementing state-of-the-art NLP models and tasks.

Example: Fine-tuning a BERT model for sentiment analysis or using GPT-3 for text generation.

Gensim: A library for topic modelling and document similarity analysis. It’s designed to process large text collections and provides algorithms like Word2Vec, Doc2Vec, and LDA (Latent Dirichlet Allocation).

Use Case: Topic modelling and semantic similarity tasks.

Example: Discovering hidden themes in a large corpus of documents or finding similar documents based on their content.

CoreNLP: Another powerful NLP toolkit developed by Stanford University. It’s Java-based and offers robust tools for performing various NLP tasks like tokenization, POS tagging, named entity recognition, parsing, sentiment analysis, and coreference resolution.

Use Case: Comprehensive text analysis and processing in Java environments.

Example: Full-fledged text analysis pipeline from tokenization to sentiment analysis in a research project.

Flair: A simple Python library for natural language processing. Built on top of PyTorch, it provides a unified interface for various word and document embeddings and a powerful framework for training and using custom models.

Use Case: Easy-to-use NLP models and embeddings.

Example: Using pre-trained word embeddings to perform named entity recognition or text classification.


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Afzal Badshah, PhD

Dr Afzal Badshah focuses on academic skills, pedagogy (teaching skills) and life skills.