🏷️ SYM: symbol

Universal Dependencies · 7 key papers · all concepts

Part of: 🗨️ Natural language processing · 🌐 Universal Dependencies

SYM (symbol) is the universal part-of-speech tag in Universal Dependencies for word-like entities that differ from ordinary words in form, function or both, such as currency signs, mathematical operators, the percent sign and emoji.

Also: symbol, UPOS SYM

What it is

In Universal Dependencies, every syntactic word gets one tag from a closed list of 17 universal part-of-speech categories (Nivre et al. 2020). SYM is the tag for symbols. These are written signs that work like words: they can be read aloud ("percent", "plus", "dollar") and can fill a slot in a phrase. They are not spelled with the ordinary letters of the language.

A symbol differs from punctuation. A punctuation mark structures or delimits text. A symbol carries content of its own. The guidelines treat SYM as part of the morphological layer of part-of-speech tagging, together with lemmas and features (Nivre et al. 2016).

Borderline cases

• SYM vs PUNCT. A hyphen or slash that joins or separates material is PUNCT. The same sign is SYM when it means "minus", "per" or "and/or".
• SYM vs NUM. Digits and numerals are NUM. A sign next to them, such as %, $ or °, is SYM.
• SYM vs NOUN. Spelled-out units ("dollars") and unit abbreviations ("km") are usually NOUN. The sign "$" is SYM.
• SYM vs X. X is reserved for material that cannot be analysed in the language, such as foreign words or fragments. Symbols are analysable, so they get SYM.
• Emoji and emoticons ("☺", ":)") are SYM, even when they work like interjections.

Features and relations

Symbols rarely inflect, so the FEATS column of a SYM token is normally empty. Treebank-specific marks such as Typo can still appear, since UD v2 introduced that feature (Nivre et al. 2020).

The dependency relation depends on what the symbol does in the sentence. An operator such as "+" or "/" between conjuncts is attached as cc. A sign standing in for a preposition ("@" for "at") is attached as case. An emoticon is attached as discourse. A percent or currency sign that heads a quantity is attached as obl or nmod, with the number depending on it.

Examples

• English: "Prices rose 5 % last year." The sign % is SYM, and 5 depends on it as a numeral modifier.
• English: "Meet me @ the station :)". Here "@" is SYM attached as case, and the smiley is SYM attached as discourse.
• English: "salt & pepper", "x = 2 + 3". These are signs read as words.
• French: "une hausse de 3 %", "10 €". The symbols head the measure phrase.
• German: "§ 5 des Gesetzes". The section sign is SYM.

Across languages

The inventory of signs is largely shared across scripts. Their syntax follows the host language, because a symbol takes the position of the word it is read as. Treebanks differ in two main ways:

• whether "$5" or "5%" is split into separate tokens during tokenization;
• whether a sign used as a conjunction is tagged SYM or CCONJ.

The relations SYM tokens take differ between languages:

The English pattern reflects web and social-media text, with its "/", "&", "@" and emoticons. The French pattern reflects measure phrases headed by % or currency signs. In both languages symbols make up only a tiny share of all tokens.

In treebanks and research

The twelve-category universal tagset of Petrov, Das and McDonald had no symbol class. Its categories were derived pragmatically from existing treebank guidelines, and stray signs fell under "." (punctuation) or X (Petrov et al. 2012). UD v1 expanded that set to 17 tags, adding PROPN and AUX among others. In doing so it separated SYM from PUNCT (Nivre et al. 2016). Its morphological features came from Interset, an interlingua of tagset drivers that decode and re-encode tags (Zeman 2008).

The theoretical account of UD treats function-like elements as dependents of content words (Marneffe et al. 2021). This explains why a symbol read as a preposition or conjunction attaches as case or cc. The principles and tooling behind these choices are also presented in tutorial form (Zeman 2021).

Because the SYM/PUNCT/X boundary rests on judgement, it is a known source of disagreement between treebanks of the same language. Consistency checks on UD corpora find annotation errors of this kind (Marneffe et al. 2017). A symmetric divergence over UPOS trigrams can flag treebank pairs whose tagging diverges, without relying on a trained tagger (Aggarwal & Zeman 2020). For dependency parsing, SYM is a small but noisy class. Errors on it mostly come from tokenization and from the cc versus punct decision.

Key papers

The works this page cites, the most cited first; citations as counted by OpenAlex plus the papers of this library that cite the work, read 2026-10-24.

Related concepts

• Universal Dependencies — Universal Dependencies is a framework and an open collection of treebanks that annotates the grammar of many languages with one shared…
• Part-of-speech tagging — Part-of-speech tagging is the task of assigning each token in a text a grammatical category, such as noun, verb, adjective or determiner…
• Morphology — Morphology is the branch of linguistics that studies the internal structure of words. It covers how words are built from meaningful units…

More papers

Topics: 🔤 Part-of-speech tagging · 🌐 Universal Dependencies

Shelves: 🗣️ Language and Linguistics

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