Jaccard similarity in NLP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is Jaccard similarity?

Jaccard similarity is a way to measure how similar two sets are. It is the size of the overlap divided by the size of the union of the sets.

beginner

How do you calculate Jaccard similarity between two sets A and B?

Jaccard similarity = (Number of elements in both A and B) / (Number of elements in A or B). In formula: |A ∩ B| / |A ∪ B|.

beginner

Why is Jaccard similarity useful in NLP?

It helps compare texts by looking at shared words or features, showing how much two texts overlap in content.

beginner

What is the Jaccard similarity between the sets {apple, banana} and {banana, cherry}?

The intersection is {banana} (1 element), the union is {apple, banana, cherry} (3 elements). So similarity = 1/3 ≈ 0.33.

beginner

Can Jaccard similarity be used for comparing sentences? How?

Yes. Convert sentences into sets of words, then calculate Jaccard similarity to see how many words they share compared to total unique words.

What does Jaccard similarity measure?

A Overlap between two sets divided by their union

B Difference between two sets

C Sum of elements in two sets

D Number of elements in the first set

Jaccard similarity measures how much two sets overlap compared to their combined size.

If two sets have no elements in common, what is their Jaccard similarity?

A 0

B 0.5

C 1

D Undefined

No overlap means intersection size is zero, so similarity is 0.

Which of these is the correct formula for Jaccard similarity?

A |A| - |B|

B |A ∪ B| / |A ∩ B|

C |A| + |B|

D |A ∩ B| / |A ∪ B|

Jaccard similarity is intersection size divided by union size.

In NLP, what do we usually compare using Jaccard similarity?

A Number of sentences

B Sets of words from texts

C Length of paragraphs

D Number of characters

We compare sets of words to see how much two texts share.

If set A = {1, 2, 3} and set B = {2, 3, 4, 5}, what is their Jaccard similarity?

A 0.6

B 0.5

C 0.4

D 0.75

Intersection is {2,3} (2 elements), union is {1,2,3,4,5} (5 elements), so 2/5 = 0.4.

Explain in your own words what Jaccard similarity is and how it can be used to compare two texts.

Think about how much two groups share compared to all items they have.

Describe how to calculate Jaccard similarity step-by-step for two example sets.

Use a simple example with fruits or numbers.