Basic Concepts
Open Class
Also known as Content Words. These are dynamic categories that readily accept new words. They carry the primary meaning of a sentence.
- Nouns: People, places, objects (e.g., algorithm)
- Verbs: Actions, states (e.g., process)
- Adjectives: Attributes (e.g., efficient)
- Adverbs: Modifiers (e.g., quickly)
Closed Class
Also known as Function Words. These have a fixed set of words and rarely change. They provide the grammatical glue of the language.
- Pronouns: Substitutes (e.g., he, it)
- Prepositions: Relationships (e.g., in, on)
- Conjunctions: Connectors (e.g., and, but)
- Determiners: Specifiers (e.g., the, a)
Key Characteristics
Dive deeper into what sets these categories apart.
Significance in NLP
Why does this distinction matter for Artificial Intelligence?
Text Analysis
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The Essence
Open class words (frequency, collocation) reveal themes, style, and tone. "Global warming" appearing often signals an environmental topic.
Summarization
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Distilling Meaning
Systems extract key content words (Nodes) to capture the gist. "Team completed project" is the core; function words just glue it together.
Sentiment Analysis
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Emotional Carriers
Adjectives and adverbs are the primary vehicles of sentiment. "Breathtakingly beautiful" carries the positive score.
Machine Translation
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Dual Strategy
Open words need Word Sense Disambiguation (meaning). Closed words need syntactic rules (structure) specific to the target language.
Information Retrieval
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Search Intent
Search engines ignore common function words ("the", "in") to focus on content words that define user intent.
Doc Classification
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Semantic Fingerprints
Open class words create a "fingerprint". Words like "blockchain" and "AI" classify a doc into Technology/Finance.
Test Your Knowledge
Classify the word below: