ToBE #3 : Curious plurals

The choice of this topic is due to my encountering 'unusual' plurals like 'datas' and 'criterias'. English is a strange language and there an no standard rules to help us learn it the right way. However, there are some general observations that work most of the time.

Plurals of words ending in 'um':
Datum-data, forum-fora, stadium-stadia, medium-media, maximum-maxima...
That holds true in most cases.
'Data' is already a plural form, so there is no such thing as 'datas'. Nobody remembers that a word 'datum' exists, so 'data' is used in the singular form also.
- Data was loaded. Data were extracted. ==> Both are accepted.
- Forums is also an accepted plural and MS-Word might correct 'fora' to 'for a'.

Plurals of words ending in 'us':
Mostly, the 'us' becomes an 'i'. Focus-foci, radius-radii, syllabus-syllabi, fungus-fungi...
- What were the foci of the meeting?
- The Class V and Class VI syllabi have changed.
For some words, adding 'es' at the end is also accepted.
Beware: Note that 'status' is both singular and plural.
- What is the status of your project?
- What are the defect status in ABC and XYZ projects? (I know it sounds odd, but that is how it is).

Plurals of words ending in 'on':
Some of them end in 'a', like: Criterion-criteria, phenomenon-phenomena, tetrahedron-tetrahedra ...
Note that 'criteria' is a plural word, hence 'criterias' is wrong. Sorry, no opinion-opinia.

Plurals of words ending in 'a':
Most people these days prefer putting an 's' at the end and that is widely accepted, but the old-order would still put an 'e' at the end: Formula-formulae, antenna-antennae, alga-algae ...

Plurals of words ending in 'is':
'is' becomes 'es'. Crisis-crises, synopsis-synopses, analysis-analyses. Note the difference in meaning and pronunciation of 'analyses' in the following:
1. Rajan analyses very well. (The stress is on 'ly')
2. Your analyses of the two topics were well-received. (Stress is on 'na', same as in analysis).