//- ----------------------------------
//- 💫 DOCS > API > LEXEME
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+section("lexeme")
    +h(2, "lexeme", "https://github.com/" + SOCIAL.github + "/spaCy/blob/master/spacy/lexeme.pyx")
        | #[+tag class] Lexeme

    p.
        The Lexeme object represents a lexical type, stored in the vocabulary –
        as opposed to a token, occurring in a document.

    p.
        Each Token object receives a reference to a lexeme object (specifically,
        it receives a pointer to a #[code LexemeC] struct). This allows features
        to be computed and saved once per type, rather than once per token. As
        job sizes grow, this amounts to substantial efficiency improvements, as
        the vocabulary size (number of types) will be much smaller than the total
        number of words processed (number of tokens).

    p.
        All Lexeme attributes are therefore context independent, as a single lexeme
        is reused for all usages of that word. Lexemes are keyed by the #[code orth]
        attribute.

    p.
        Most Lexeme attributes can be set, with the exception of the primary key,
        #[code orth]. Assigning to an attribute of the #[code Lexeme] object writes
        to the underlying struct, so all tokens that are backed by that
        #[code Lexeme] will inherit the new value.

    +code("python", "Overview").
        class Lexeme:
            def __init__(self, vocab, key):
                return self

            int rank

            int orth, lower, shape, prefix, suffix

            unicode orth_, lower_, shape_, prefix_, suffix_

            bool is_alpha, is_ascii, is_lower, is_title, is_punct, is_space, like_url, like_num, like_email, is_oov, is_stop

            float prob
            int cluster
            numpy.ndarray[float64] vector
            bool has_vector

            def set_flag(self, flag_id, value):
                return None

            def check_flag(self, flag_id):
                return bool

            def similarity(self, other):
                return float

    +table(["Example", "Description"])
        +row
            +cell #[code.lang-python lexeme = nlp.vocab[string]]
            +cell Lookup by string
        +row
            +cell #[code.lang-python lexeme = vocab[i]]
            +cell Lookup by integer

    +section("lexeme-stringfeatures")
        +h(3, "lexeme-stringfeatures").
            String Features

        +table(["Name", "Description"])
            +row
                +cell orth / orth_
                +cell.
                    The form of the word with no string normalization or processing,
                    as it appears in the string, without trailing whitespace.

            +row
                +cell lower / lower_
                +cell.
                    The form of the word, but forced to lower-case, i.e.
                    #[code lower = word.orth_.lower()]

            +row
                +cell shape / shape_
                +cell.
                    A transform of the word's string, to show orthographic features.
                    The characters a-z are mapped to x, A-Z is mapped to X, 0-9
                    is mapped to d. After these mappings, sequences of 4 or more
                    of the same character are truncated to length 4. Examples:
                    C3Po --> XdXx, favorite --> xxxx, :) --> :)

            +row
                +cell prefix / prefix_
                +cell.
                    A length-N substring from the start of the word. Length may
                    vary by language; currently for English n=1, i.e.
                    #[code prefix = word.orth_[:1]]

            +row
                +cell suffix / suffix_
                +cell.
                    A length-N substring from the end of the word. Length may vary
                    by language; currently for English n=3, i.e.
                    #[code suffix = word.orth_[-3:]]

    +section("lexeme-booleanflags")
        +h(3, "lexeme-booleanflags")
            | Boolean Flags

        +table(["Name", "Description"])
            +row
                +cell is_alpha
                +cell Equivalent to #[code word.orth_.isalpha()]

            +row
                +cell is_ascii
                +cell Equivalent to any(ord(c) >= 128 for c in word.orth_)]

            +row
                +cell is_digit
                +cell Equivalent to #[code word.orth_.isdigit()]

            +row
                +cell is_lower
                +cell Equivalent to #[code word.orth_.islower()]

            +row
                +cell is_title
                +cell Equivalent to #[code word.orth_.istitle()]

            +row
                +cell is_punct
                +cell Equivalent to #[code word.orth_.ispunct()]

            +row
                +cell is_space
                +cell Equivalent to #[code word.orth_.isspace()]

            +row
                +cell like_url
                +cell Does the word resemble a URL?

            +row
                +cell like_num
                +cell Does the word represent a number? e.g. “10.9”, “10”, “ten”, etc.

            +row
                +cell like_email
                +cell Does the word resemble an email?

            +row
                +cell is_oov
                +cell Is the word out-of-vocabulary?

            +row
                +cell is_stop
                +cell.
                    Is the word part of a "stop list"? Stop lists are used to
                    improve the quality of topic models, by filtering out common,
                    domain-general words.

    +section("lexeme-distributional")
        +h(3, "lexeme-distributional")
            | Distributional Features

        +table(["Name", "Description"])
            +row
                +cell prob
                +cell.
                    The unigram log-probability of the word, estimated from
                    counts from a large corpus, smoothed using Simple Good Turing
                    estimation.

            +row
                +cell cluster
                +cell.
                    The Brown cluster ID of the word. These are often useful features
                    for linear models. If you’re using a non-linear model, particularly
                    a neural net or random forest, consider using the real-valued
                    word representation vector, in #[code Token.repvec], instead.

            +row
                +cell vector
                +cell.
                    A "word embedding" representation: a dense real-valued vector
                    that supports similarity queries between words. By default,
                    spaCy currently loads vectors produced by the Levy and
                    Goldberg (2014) dependency-based word2vec model.

            +row
                +cell has_vector
                +cell.
                    A boolean value indicating whether a vector.