Learn English – How to pronounce bechamel the English way

In normal speech, I would say "that is." I would not say "eye ee" for a couple of reasons.

• The audience may not actually know what "eye ee" means.
• It could be ambiguous because another term IE could mean something other than "that is". Consider a speech about web browsers. The audience would not know what you are referring to when you say "eye ee". Is that i.e. or is that Internet Explorer? The audience can probably come to the conclusion of which one it is, but for clarity, you should say "that is".
• Public speakers do not usually say i.e., so you should follow that convention.

While reading i.e. from text, I still say "that is." It is the same with e.g., I would say "for example." However, it is not incorrect to say "eye ee" since you, yourself know what the context is, it is fine.

To summarize, it is very common to say "that is". If you are reading aloud to listeners who are unable to see the text, I would recommend saying "that is" to avoid any ambiguity. If they can see the text and clearly know that you are conveying the abbreviation i.e, you can say "eye ee". If you prefer, you can say the full latin: id est

The answer is all of the above, any of the above, or none of the above. There is no single set of rules for the pronunciation of taxa, and no single interpretation of such rules as some have attempted to compile. As Michael G. Simpson notes under "Pronunciation of Names" in Plant Systematics (2006),

Although scientific names are universal, their pronunciations may vary from region to region, especially between different countries. For example, European pronunciations are often different from those of most American botanists. There are no firm rules as to how scientific names should be pronounced. Very often, pronunciations are influenced by one's native language. One should be flexible and adaptive with regard to pronunciations, as the overriding goal is communications.

Broadly, most English-speaking practitioners of science, medicine, law, architecture, and other disciplines follow traditional English pronunciation of Latin for the Latin and quasi-Latin terms in their fields. There are those who push for what is known as Reformed Academic Pronunciation, a system devised in the late 19th century which is supposed to be closer to the classical pronunciation, and which is closer to the way the words would be pronounced in most continental European languages. William Stearn favors the latter in his widely cited Botanical Latin (1983), but as countless papers, guides, and appendices note:

• Professionals not only use different pronunciations from one place to another, but do not consistently follow the same system themselves.
• People tend to pronounce names based on how they first hear them, as opposed to a particular system of pronunciation
• English speakers don't agree on how to pronounce English; how would they agree on how to pronounce any other language or pseudo-language? (Yes, I am one of those people who is always going on about bruschetta— it's Italian, not French or German.)

Zoologists and bacteriologists moved away from requiring a classical basis for names some time ago, and botanists have moved in the same direction, so perhaps there will be less debate in the future.