Semantic Similarity
A measure used in natural language processing to determine how similar two texts are in meaning.
What Is Semantic Similarity
Semantic similarity measures how close two words, phrases, or longer texts are in meaning. Unlike exact string matching, semantic methods can identify related meaning even when vocabulary or sentence structure differs.
Why Semantic Similarity Matters in NLP
Many NLP tasks depend on meaning based comparison rather than literal overlap. Semantic similarity improves retrieval, clustering, duplicate detection, and relevance ranking because it focuses on conceptual closeness between texts.
- better matching for paraphrased content
- more accurate intent and topic grouping
- improved robustness across domains and writing styles
Methods for Measuring Semantic Similarity
Common methods include:
- vector embeddings with cosine similarity
- transformer based sentence encoders
- cross encoder scoring models for pairwise comparison
- hybrid approaches combining lexical and semantic signals
Method choice depends on speed requirements, language coverage, and evaluation quality targets.
Applications in Machine Translation and Translation Quality Evaluation
In translation, semantic similarity helps compare generated output with reference translations when wording differs but meaning is preserved. This is valuable for quality estimation, candidate reranking, and post editing prioritisation.
- evaluating adequacy beyond exact n-gram overlap
- detecting meaning drift in MT outputs
- supporting bilingual retrieval and terminology validation
Examples of Semantic Similarity in Practice
For example, the sentences “The contract was terminated” and “The agreement was cancelled” share close meaning despite different wording. A semantic similarity model should score this pair higher than unrelated pairs, helping reviewers and AI systems focus on true meaning preservation.
Related Terms
Segment-based Translation
Translation performed segment by segment rather than on the full document.
Speech Recognition
Technology that converts spoken language into written text using machine learning models.
Style Guide
A document defining linguistic, stylistic, and formatting rules for translation.
Supervised Learning
A machine learning method in which models are trained using labelled data.
Sustainability of AI Systems
Practices aimed at reducing the environmental and computational impact of AI.
Related Resources
Natural Language Processing (NLP)
A field of artificial intelligence focused on enabling computers to understand, analyse, and generate human language.
Token
A unit of text processed by a model, such as a word, subword, or punctuation mark.
Named Entity Recognition (NER)
A natural language processing method used to identify and classify entities such as names, organisations, locations, and dates in text.
Large Language Model (LLM)
A neural model trained on vast text corpora, capable of understanding and generating natural language.
Prompt Engineering
The practice of designing and structuring prompts to obtain more accurate and useful outputs from AI models.
Bilingual Corpus
A collection of aligned texts in two languages used to train, evaluate, or improve translation systems and language technologies.