Abbreviating words can slow development and add uncertainty. This is because vowels and correct spelling improve comprehension. So it is good practice to leave full words in the code where possible and be consistent with your usage.
Abbreviation can be tempting when the word is very long but usually truncation of the word works better than abbreviation. Remember that your personal idea of how an abbreviation should work will rarely match someone else's , so it is better not to abbreviate at all.
However there are some widely used abbreviations for long words that have become acceptable. You should restrict yourself to a small set like this one:
avg (matches min/max/avg)
index,i,j,k (not lower case L because it looks like a 1)
max (matches min/max/avg)
msecs or millis
min (matches min/max/avg)
param or parm
Abbreviations that never caught on:
Why not “buf” or buffer?
Why a removal and replacement of some letters but not others?
Is it Statistics or State or Status?
Is it Microgram or Milligram? This confusion has killed when used for prescriptions.
Assistants would rather be called Assistants.
To save just eight vowels, readability is compromised.
Uses unprofessional “leet-speak” to substitute a word with a number. Don't use leet-speak at all in professional work.
Summary: Use full words rather than abbreviate. Be consistent. Follow only the common set of abbreviations, don't make up your own.