Natural Language Processing · M2 · papers

Q3B · Lesk word-sense disambiguation

Solved re-exam · February 2026

M2-relevant questions from an actual TEE paper · original marks retained for longer practice

Question. Consider the sentence: “The bank can ensure your deposits are safe.” The word “bank” has the following two possible senses (WordNet-style glosses):
Bank₁: Sloping land especially beside a body of water.
Bank₂: A financial institution that accepts deposits and channels the money into lending activities.
i. Apply the LESK algorithm to determine the correct sense of the word “bank” in the given sentence. Show the steps clearly.
ii. Briefly discuss limitations of the LESK algorithm in handling ambiguous words in real-world contexts. [10 marks]

Answer

Given

Context sentence and the two supplied dictionary glosses. Use a simplified Lesk method: lowercase, remove function words, exclude the target bank and compare distinct content-word overlap. Do not add synonyms that the question does not supply.

To find

Which candidate gloss has the greatest overlap with the local context.

Formula: which one and why

\mathrm{score}(s)=|C\cap G_s|,\qquad \hat s=\arg\max_s\mathrm{score}(s)

C is the set of context content words. Gₛ is the content-word set of the gloss for sense s. The intersection contains words appearing in both; its size is the score. This is an overlap count, not a probability.

Solution

Step 1. Prepare the context

Remove The, can, your, are and the target bank. A reasonable content set is C = {ensure, deposits, safe}. If “can” is retained under another fixed stop-list it matches neither gloss and does not change the result.

Step 2. Prepare Bank₁’s gloss

G₁ = {sloping, land, especially, beside, body, water}. There is no shared word with {ensure, deposits, safe}.

Step 3. Calculate Bank₁’s score

C\cap G_1=\varnothing,\qquad \mathrm{score}(1)=0

Step 4. Prepare Bank₂’s gloss and count overlap

G₂ = {financial, institution, accepts, deposits, channels, money, lending, activities}. The shared word is deposits.

Step 5. Calculate Bank₂’s score and select

C\cap G_2=\{\mathrm{deposits}\},\qquad \mathrm{score}(2)=1

1 > 0, so choose the financial-institution sense.

Final answer

Bank₂: financial institution. The explicit overlap “deposits” supports this choice.

Yaad rakho: Lesk: context aur har meaning ki definition mein common words count karo; highest overlap choose karo.

ii. Limitations

Short contexts or short glosses may produce no overlaps or ties.
Exact word matching misses related words and synonyms, such as deposit versus savings, unless an extension is defined.
Irrelevant frequent words can create misleading overlaps if preprocessing is poor.
Dictionary glosses may omit a domain-specific sense or fail to express the context’s wording.
Simplified Lesk uses limited local information and may miss discourse or real-world knowledge.

Lemmatization, richer glosses and semantic similarity can improve variants, but the exact variant and tie-breaking rule should be stated.