that
conj.a word used to connect a main part of a sentence to a new clause that adds more information. You use it to introduce what someone says, thinks, or feels.
conj.introduces a subordinate clause that functions as the object or complement of a verb, adjective, or noun. Often omitted in informal spoken registers when the meaning remains clear.
“I hope that you have a great day.”
“The scientist argued that the new data would change how we understand the history of the planet.”
“The prevailing philosophical consensus suggests that human consciousness is not a singular entity but rather a complex series of interconnected cognitive processes occurring simultaneously.”
Often functions as a complementizer; it can be omitted in informal contexts ('I think that it's raining' vs 'I think it's raining').
The verb 'tell' requires a personal object (e.g., 'He told me that...') whereas 'say' can be followed directly by a 'that' clause.
From Middle English that, from Old English þæt (“the, that”, neuter definite article and relative pronoun), from Proto-West Germanic þat, from Proto-Germanic þat. Cognate to Scots that, Saterland Frisian dät, West Frisian dat, Dutch dat, Low German dat and datt, German dass and das, Danish det, Swedish det, Icelandic það, Gothic 𐌸𐌰𐍄𐌰 (þata). Further from Proto-Indo-European *tód; compare Ancient Greek τό (tó), Sanskrit तद् (tád), Waigali ta, Lithuanian tai̇̃, Polish to.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.
For Spanish speakers Spanish lacks the /ð/ phoneme in word-initial positions, so speakers often substitute the dental /d/ used in 'dedo', resulting in a lack of the characteristic friction of the English voiced dental fricative.
Spanish 'que' is obligatory before a subordinate clause ('espero que vengas'), whereas English often prefers an infinitive. The transfer over-inserts 'that', producing 'I want that you come' for 'I want you to come'.
For Mandarin speakers In Mandarin, object clauses are often juxtaposed without a marker, as in '我看他说 (Wǒ kàn tā shuō)'. Because the linking function is implicit in the L1, learners frequently omit the subordinating conjunction 'that' in formal contexts where it is stylistically preferred or grammatically required to clarify the sentence structure.
For Japanese speakers Japanese syntax is head-final, placing the subordinate clause before the main verb without a linking particle equivalent to 'that'. Because Japanese lacks an overt complementizer between the matrix and subordinate clauses, learners often omit 'that' or lose the structural connection in complex reporting sentences.
The Japanese reporting particle 'と' (to) is used for both direct and indirect speech. This leads learners to over-insert 'that' before direct quotes (e.g., 'He said that "I am hungry"') or use it with verbs that do not take 'that'-clauses in English, like 'tell' without a person object.
For French speakers French speakers often substitute the dental fricative /ð/ with /z/ or /d/, as the voiced 'th' sound does not exist in the French phonological system.
French requires the subordinator 'que' in all contexts, leading learners to over-insert 'that' in English sentences where the conjunction is optionally omitted, such as 'I think (that) he is here'.