In Information Retrieval Systems:

1. Case-folding can lower precision.

2. Stemming decreases the length of the postings list.

3. Soundex encoding improves recall.

4. Cosine similarity metric is better than Euclidean distance metric for relevance ranking because it can distinguish documents that have different lengths such as a technical article and its summary.

Precision is defined as the number of relevant documents retrieved by a search divided by the total number of documents retrieved by that search. Recall is defined as the number of relevant documents retrieved by a search divided by the total number of existing relevant documents (which should have been retrieved).