1.Overview

The wordnet is semantically oriented dictionary of English.

2.Senses and Synonyms

Accessing synonyms as bellow:

from nltk.corpus import wordnet

#return the synset that word 'motorcar' belong to.
wordnet.synsets('motorcar')

#return the list of lemma names about 'car.n.01'
wordnet.synset('car.n.01').lemma_names
#return the list of lemma about 'car.n.01'
wordnet.synset('car.n.01').lemma

#return string of definition of 'car.n.01'
wordnet.synset('car.n.01').definition

#return the example sentence of 'car.n.01'
wordnet.synset('car.n.01').examples

3.The WordNet Hierarchy

The relationship of father & child(is-a) As shown as bellow:

Accessing hyponyms as bellow:

from nltk.corpus import wordnet

motorcar = wordnet.synset('car.n.01')
sub_motorcars = motorcar.hyponyms()

#get sorted hyponyms names of 'car.n.01'
sub_names = [lemma.name for synset in sub_motorcars for lemma in synset.lemmas]

Accessing hypernyms as bellow:

from nltk.corpus import wordnet

motorcar = wordnet.synset('car.n.01')

#get the hypernym of 'car.n.01'
father = motorcar.hypernyms()

#get the upper path of 'car.n.01'
paths = motorcar.hypernym_paths()

#get the root of 'car.n.01'
root = motorcar.root_hypernyms()

4.More Lexical Relations

4.1.The relationship of meronyms & holonyms(part-of).

Accessing as bellow:

from nltk.corpus import wordnet

#get the meronyms about 'tree.n.01'
wordnet.synset('tree.n.01').part_meronyms()

#get the meronyms about 'tree.n.01'
wordnet.synset('tree.n.01').substance_meronyms()

#get the holonyms about 'tree.n.01'
wordnet.synset('tree.n.01').member_holonyms()

#get the holonyms about 'tree.n.01'
wordnet.synset('tree.n.01').part_holonyms()

#get the holonyms about 'tree.n.01'
wordnet.synset('tree.n.01').substance_holonyms()

4.2.The relationship between verbs

The entailments of verb. Accessing as bellow:

from nltk.corpus import wordnet

#get the entailments of a verb
wordnet.synset('walk.v.01').entailments()

4.3.The relationship of antonymy

To accessing antonym as bellow:

from nltk.corpus import wordnet

wordnet.lemma('horizontal.a.01.horizontal').antonyms()

5.For more relationship of WordNet

You can see more relationships & API of synset by dir(),such as:

dir(wordnet.synset('harmony.n.02'))

6.Semantic Similarity

6.1.Common Father’s Depth

If two synset share a very specific hypernym,they are very semantic similary. Accessing the lowest common father as bellow:

from nltk.corpus import wordnet

right_whale = wordnet.synset('right_whale.n.01')
orca = wordnet.synset('orca.n.01')

#get the lowest common father of 'right_whale.n.01' & 'orca.n.01'
right_whale.lowest_common_hypernyms(orca)
#get the depth of common father in wordnet
right_whale.lowest_common_hypernyms(orca).min_depth()

6.2.Length of Connection

If two word connected in a short way in the wordnet,the are very semantic similar. Accessing the length of connection of two words as bellow:

from nltk.corpus import wordnet

right_whale = wordnet.synset('right_whale.n.01')
orca = wordnet.synset('orca.n.01')

#get the similarity measured by length of connection of two words.
#return (0,1] or -1 when no connection between two words.
right_whale.path_similarity(orca)