I have read through the info on this site and other promotion sites and sometimes the info has been conflicting or unclear. Thus I still have some unresolved questions about Meta keywords:
1. Plurals. I understand that it would be beneficial to include cactus and cacti, but what about words that just have 's' appended to them? Will the search engine automatically find the singular form from the plural? For example, is it better to list both forms of the word (e.g., 'apple, apples'), or just the plural form (e.g., 'apples').
2. Phrases. If a particular word appears in a number of different (legitimate) phrases, would they count that as spamming? For example, 'fishing, fishing tackle, fishing lures, fishing rods'. It seems to me that, in this example, just using the words 'tackle' & 'rods' would not necessarily yield an accurate search because those words could be used for a number of different applications.
3. Word stems. Do the search engines count word stems when counting for spam? For example, would the words 'fish, fishing, fisherman' count as three instances of 'fish'?
4. Limits. Are keyword lists limited by number of words or number of characters? What are the limits?