Pronunciation: [ðˈat ɪz] (IPA) 
The spelling of the phrase "that is" is straightforward. It consists of two words, "that" and "is," with a stressed syllable on the second syllable of "is." In IPA phonetic transcription, the word "that" is pronounced /ðæt/, while "is" is pronounced /ɪz/. When spoken together, the stress falls on the second syllable of "is," resulting in the phonetic transcription /ðæt ɪz/. When written, the phrase is simply spelled "that is."
That is is a transitional phrase used to introduce or clarify a statement by providing further explanation, elaboration, or clarification. It is often used to restate or summarize a point made previously, or to provide additional relevant information or examples. The phrase is commonly used in both written and spoken English to emphasize a specific point or to provide an example that supports a previous statement.
In conversation, that is can be used to paraphrase or rephrase a previous statement for clarity. It can also be used to introduce an example or an illustration that strengthens the argument or provides evidence for a point. In writing, that is is frequently used to sum up a concept or idea discussed earlier, reinforcing the message or making it more understandable.
Moreover, that is can be used to emphasize the conclusion or the result of something, often expressing a cause-and-effect relationship. It can also be used in a contrasting sense to differentiate between two or more possibilities or choices. Additionally, that is can be utilized to add more information, clarification, or to offer a contrasting opinion in a discussion or debate.
Overall, that is serves as a valuable linguistic tool in communication, aiding in the expression of thoughts and ideas in a concise, clear, and coherent manner.
* The statistics data for these misspellings percentages are collected from over 15,411,110 spell check sessions on www.spellchecker.net from Jan 2010 - Jun 2012.
The etymology of the phrase "that is" can be traced back to Old English. In Old English, the word for "that" was commonly spelled as "þæt", and it essentially meant "the or that". Similarly, the word for "is" in Old English was often spelled as "eart" or "ys". Over time, these words gradually transformed and evolved into their modern forms. The phrase "that is" is commonly used as a way to explain or provide further information about something that has been previously mentioned.
