Scalar, adj. and n.

Pronounciation:

/ˈskeɪlə/, /ˈskeɪlɑː/

Meaning:

Noun: In quaternions, a real number. More widely, a quantity having magnitude but no direction, and representable by a single real number.

Adjective: Of the nature of a scalar.

Source:

OED

A singular matrix is a matrix which is not invertible.

The singular values of a matrix A∈ ℂ^(n x m) are the square roots of eigenvalues of A*A.

source 

A singular value decomposition of a complex mxn matrix A is three matrices U, V, ∑, where U is an mxm complex unitary matrix, V is an nxn complex unitary matrix, and ∑ is an mxn diagonal matrix with non-negative real values on the diagonal, such that A=U∑V*.

source 

 /ˈsʌbˌɡruːp/

Let (G, *, ',e) be a group. Let H be a subset of G. We say, that H is a subgroup of G if e is element of H, and for every a,b elements of H are a*b and a' elements of H.

For pronunciation: https://dictionary.cambridge.org/dictionary/english/subgroup 

Noun
Prefix: sur-

Pronunciation
/səːˈdʒɛkʃən/ listen

Meaning
A class of functions whose each element of codomain is mapped to by at least one element of the domain, i.e. the image and the codomain of the function are equal.

Example

Synonyms
Surjective function, onto mapping, onto

Similar words
Surjective adjective /səː'dʒɛktɪv/ listen

Etymology
The term introduced by Nicolas Bourbaki. The prefix sur- means over, above.

Source
OED