Hello Denise Latreille ,

I have not seen this issue before so a did a little testing and was eventually able to reproduce this 

So far so good.

Now I notice if i click 'Full Form'

then 'NULL' is indeed removed -

If you ensure FULL FORM is not active, then you can add the terms you wish without further issue

Hello Denise Latreille

I was actually just playing with this example to understand why this happens and have an example here

It seems that you can add 'null' ONLY if part of this is capitalised- AnNULLable or even AnNullable

The only way it appears to possible to add the term you want exactly is to export your Termbase to Excel (using the Glossary Converter) add the new Term and then convert back to SDLTB using the Glossary Converter....

Then the term is available as you need it to be.

The problem appears to be that 'null' is a command in MultiTerm- which means it is simply ignored by MT ( null=zero) and looks like to be a bug.

Hello Denise Latreille (DeniseLatreille),

Please try to add the new terms that include "null" with "Flags Layout" and not with the Default Layout" and will work:

I came across this same problem. In one of my glossaries I entered "null hypothesis", only to find later that MultiTerm deleted "null" and left just "hypothesis". It also deletes the word null inside descriptive fields (!). For instance, I tried to circumvent this issue by putting the word null between single quotes ('null') or even between dashes (-null-), and then MultiTerm will leave for instance '' hypothesis or -- hypothesis.   Using the Flag Layout will accept entries with the word "null" included. The Full Form input model issue, referenced above, does not work. This is a bug probably related to the fact that  Null is a reserved word within the world of programming but somehow MultiTerm, when parsing a string of text it is considering the word null as a reserved word, go figure. 

However, although you can add a term that contains the word 'null' using the Flag Layout, once you switch to the Default Layout (this is MultiTerm 2017 and MultiTerm 2019) your entry with the word "null" will have that word suppressed. I just saw it. In entered "null hypothesis" with the Flag Layout, no problem. Then, after switching to Default Layout, bang!, the entry became just "hypothesis" (!). In addition, my termbase is messed up. The entry in question, ended up replacing the entry numbered 1. I have to recognize that before that, I was editing the  definition of my termbase, adding some descriptive fields at different levels here and there.This is a bug! 

I certainly agree with you. I've worked in the computer business for years, and even if NULL is a reserved word for MultiTerm, they can find a work-around or reject the word as it is keyed in.

Totally aggree. Cheers!