Understanding the Basics of NLP: Text Preprocessing, Tokenization, and Stemming

Are you tired of sifting through massive amounts of text to find the information you need? Do you wish there was a way to make sense of all the written content out there? Well, look no further than natural language processing (NLP)!

NLP is a field of study that uses algorithms and computational models to analyze, understand, and generate human language. NLP allows computers to process natural language text and identify patterns, meaning, and sentiment within it. In this article, we will explore some of the fundamental concepts of NLP that help make this possible: text preprocessing, tokenization, and stemming.

Text Preprocessing

Text preprocessing is a crucial step in NLP, as it helps to prepare text data for analysis. The main goal of text preprocessing is to clean and standardize text to make it easier for computers to process. This involves a variety of tasks, including:

Removing Punctuation and Special Characters

Before computers can analyze text data, they need to be able to parse it effectively. One of the first steps in text preprocessing is to remove any punctuation or special characters that might interfere with parsing. This might include commas, periods, question marks, and exclamation points, as well as less common characters like semicolons, em dashes, and ellipses.


Another common preprocessing step is to convert all text to lowercase. This helps to standardize the data and make it easier for computers to match words and identify patterns within the text. However, it is worth noting that there are exceptions to this rule – for example, proper nouns like names and titles should not be lowercase.

Removing Stop Words

Stop words are words that occur frequently in text but do not carry much meaning on their own, such as “the”, “of”, and “and”. These words might be useful for readability and natural language purposes, but for NLP analyses, they can add noise to the data and make it more difficult to identify meaningful patterns. Therefore, it is often helpful to remove stop words during text preprocessing.

Normalizing Words

Another important task in text preprocessing is to normalize words. This means converting different forms of the same word into a standard form – for example, converting “walk”, “walked”, and “walking” to the base form “walk”. This helps to reduce the number of unique words in the data and make it easier to identify common patterns.

Removing HTML Tags

If you are working with text data that was scraped from the web, you may need to remove HTML tags and other markup language from the text data. This is because HTML code can add noise to the data and make it more difficult to analyze.


Now that we have cleaned and standardized our text data through text preprocessing, we can move on to the next step: tokenization. Tokenization is the process of breaking down text into smaller, meaningful pieces called tokens. These tokens might be words, phrases, or even individual characters, depending on the goals of the analysis.

Word Tokenization

The most common type of tokenization is word tokenization, which involves breaking down text into individual words. This is a crucial step in many NLP analyses, as it allows us to perform analyses like word frequency counts and sentiment analysis.

For example, consider this sentence:

“The quick brown fox jumps over the lazy dog.”

Using word tokenization, we can break this sentence down into the following tokens:

“The”, “quick”, “brown”, “fox”, “jumps”, “over”, “the”, “lazy”, “dog”.

Phrase Tokenization

In some cases, it may be useful to tokenize text into larger phrases or chunks, rather than individual words. This might be helpful, for example, if you are interested in analyzing specific phrases like product names or job titles within a larger set of text.

Character Tokenization

Finally, it is worth noting that tokenization can also be done at the character level. This involves breaking down text into individual letters or symbols, and might be useful for tasks like handwriting recognition or language modeling.


The final concept we will explore in this article is stemming. Stemming is the process of reducing a word to its base or root form, in order to normalize variations and make it easier to analyze patterns in the data.

Porter Stemming Algorithm

One of the most well-known stemming algorithms is the Porter stemming algorithm, developed by Martin Porter in the 1970s. This algorithm works by iteratively removing suffixes from words until it reaches the base form.

For example, consider the following words:

“walking”, “walked”, “walks”

Using the Porter stemming algorithm, we can reduce these words to their base form, “walk”. This can be helpful for tasks like keyword extraction, where you want to identify the most common or relevant words in a set of text data.

Snowball Stemming Algorithm

Another popular stemming algorithm is the Snowball stemming algorithm, which is based on the Porter algorithm but offers additional language support for languages beyond English.


In this article, we have explored some of the key concepts of NLP, including text preprocessing, tokenization, and stemming. These processes are critical for making sense of the vast amounts of natural language data that exist online, and can help us to extract meaningful insights and identify patterns within that data. By understanding the basics of NLP, we can empower ourselves to tackle complex language processing tasks and build powerful tools and applications that make our lives easier.

Editor Recommended Sites

AI and Tech News
Best Online AI Courses
Classic Writing Analysis
Tears of the Kingdom Roleplay
Database Ops - Liquibase best practice for cloud & Flyway best practice for cloud: Best practice using Liquibase and Flyway for database operations. Query cloud resources with chatGPT
Learn Snowflake: Learn the snowflake data warehouse for AWS and GCP, course by an Ex-Google engineer
Haskell Community: Haskell Programming community websites. Discuss haskell best practice and get help
Haskell Programming: Learn haskell programming language. Best practice and getting started guides
Cloud events - Data movement on the cloud: All things related to event callbacks, lambdas, pubsub, kafka, SQS, sns, kinesis, step functions