What is the difference between tenant improvement and leasehold improvements?

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An excerpt:

What's the difference between tenant improvements ("TI,") "leasehold improvements," and "build-out" in a commercial business lease? 
Basically, no difference. It just depends on what industry you are in or who is looking at the issue. All three terms mean work that is done to an office or building to prepare it for the needs of a new tenant. 
The term TI or "tenant improvements" (used by commercial realtors) can also be expressed from an accounting viewpoint as "leasehold improvements," and from a construction viewpoint as "build-out." I have heard different professions use these terms; leasing companies and property management companies and commercial Realtors talk about TI or build-out; accountants talk about leasehold improvements
For the purposes of this article, I will use the term "leasehold improvements," because that's the term used most often in business accounting, record keeping, and taxes.