It's Greek to Me

Greek letters

The Greek letters that are most often confused with Latin letters are:  β/B, ε/e, η/n, ι/i, κ/K, ν/V, ρ/p, τ/T, υ/u, χ/x, ω/w. 

The Greek letters I most commonly use in these web pages are, in order α β φ γ Γ Σ ε Φ δ χ Δ θ ω λ

Lower
case
Upper
case
Name in
English
American pronunciation cue
α Α alpha Like calendar, not like all
β Β beta Like bay, not like bee
γ Γ gamma Like ham
δ Δ delta Like bell
ε Ε epsilon Like step
ζ Ζ zeta Like bay
η Η eta Like bay
θ Θ theta Like bay; unvoiced th like thick, not like they
ι Ι iota Like eye then owe; stress on o
κ Κ kappa Like gap
λ Λ lambda Like lamb
μ Μ mu Like m followed by you, or (less commonly) moo
ν Ν nu Like zoo, no y sound
ξ Ξ xi Like z followed by eye, or k followed by sigh
ο Ο omicron Like ah, middle, on; stress on o
π Π pi Like pie
ρ Ρ rho Like row
σ Σ sigma Like signal
τ Τ tau Like cow
υ Υ upsilon Like oops; stress on up
φ Φ phi Like file
χ Χ chi Like k followed by eye
ψ Ψ psi Like p followed by sigh
ω Ω omega Like oh, may; stress on me

It makes no sense to stress the o in omicron ("little O") but not in omega ("big O"), but there you are, that's what Americans seem to do.  British pronunciation is at least consistent:  omicron (oh-my-kron). 

Words of Greek origin are often proparoxytone, that is, pronounced with the main stress on the second-to-last syllable.  Examples (besides proparoxytone itself) are analyses, automata, criterion, and schemata

Other symbols and words that often cause problems

Ab
Usually things like this are pronounced "A sub b". 
A, a
If both cases appear in the same equation, it is common to hear people say "big A" and "A" (but usually not "little A" except for emphasis). 
analyses
Plural of analysis.  One analysis, two analyses.  Pronounced "an-AL-is-eez".  Of Greek origin (thus the plural and the stress on the third-to-last syllable). 
automata
The plural of automaton.  One automaton, two automata.  It is somewhat rare to see automatons.  Of Greek origin (αυτοματον).
axes
Plural of axis.  One axis, two axes.  Pronounced "AX-eez".  Of Latin origin (but probably originally Greek). 
complement
Sometimes confused with the related word "compliment".  Mathematical uses take "complement" spelled with the 'e'. 
correspondence
Sometimes confused with the related word "correspondance".  Mathematical uses take "correspondence" spelled with the 'e'. 
criterion / criteria
One criterion, two criteria.  The OED mentions 'criterions' as 'uncommon' (it's very uncommon).  There is no such word as 'criterias'. Of Greek origin. 
extremum / extrema
One extremum, two extrema.  It is rare to see extremums Of Latin origin.
rational vs. rationale
A number can be rational (if it's the ratio of two integers);  a person can be rational (if he or she is thinking logically and clearly), his or her argument can be rational (if it's clear and logical), and a choice he or she makes can be rational (if the argument in favor of that choice is clear, cogent, and more convincing than the arguments for the alternative choices. 

However, the reasons for making a choice are its rationale.  Pronounced RA-shu-NAAL.  Rhymes with "pal" and "shall", but the "nale" syllable lasts a little longer. 

schemata
The plural of schema (although schemas is also common).  One schema, two schemata.  Of Greek origin (σχημα), thus the plural in -ta and the stress on the third-to-last syllable sche, like automaton is also stressed on its third-to-last. 
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2009Sep23We10:12
Thomas A. Alspaugh