My question is generally on Singular Value Decomposition (SVD), and particularly on Latent Semantic Indexing (LSI).

Say, I have $ A_{word \times document} $ that contains frequencies of 5 words for 7 documents.

A =  matrix(data=c(2,0,8,6,0,3,1,
                   1,6,0,1,7,0,1,
                   5,0,7,4,0,5,6,
                   7,0,8,5,0,8,5,
                   0,10,0,0,7,0,0), ncol=7, byrow=TRUE)
rownames(A) <- c('doctor','car','nurse','hospital','wheel')

I get the matrix factorization for $A$ by using SVD: $A = U \cdot D \cdot V^T $.

s = svd(A)
D = diag(s$d) # singular value matrix
S = diag(s$d^0.5 ) # diag matrix with square roots of singular values.

In 1 and 2, it is stated that:

$WordSim = U \cdot S$ gives the word similarity matrix, where the rows of $WordSim $ represent different words.

WordSim = s$u %*% S

$DocSim= D \cdot V^T$ gives the document similarity matrix where the columns of $DocSim$ represent different documents.

DocSim = S %*% t(s$v)

Questions:

1. Algebraically, why are $WordSim$ and $DocSimS$ word/document similarity matrices? Is there an intuitive explanation?
2. Based on the R example given, can we make any intuitive word count / similarity observations by just looking at $WordSim$ and $DocSim$ (without using cosine similarity or correlation coefficient between rows / columns)?