Learn English – What’s the difference between “lonely” and “lonesome”

The OED gives the following definitions of reliable and dependable:

Reliable—1. That may be relied on.

1a. Of a person, information, etc.: able to be trusted; in which reliance or confidence may be placed; trustworthy, safe, sure.

1b. orig. U.S. Of a product, service, etc.: consistently good in quality or performance; dependable.

Dependable—That may be depended on; trustworthy, reliable.

Both definitions list the other word in their definitions, with no special qualifiers attached. In addition, both words use the word trustworthy, also without qualifiers. Therefore, it is safe to say that the two are synonyms and may be equally used.

1. Suasive is an adjective that, in Linguistics (Grammar), "denotes a class of English verbs, for example, insist, whose meaning includes the notion of persuading and that take a subordinate clause whose verb may either be in the subjunctive or take a modal."

2. Persuasive is an adjective as well, that means being "good at persuading someone to do or believe something through reasoning or the use of temptation: an informative and persuasive speech." OR "She was very persuasive!"

The difference, then, is that while the former denotes a grammatical class for verbs, the second is adopted the way you already know, with people, situations, etc.

EDIT NOTE: In the OED it says that a speech can be "suasive" but considering the OALD and my dictionary didn't have it, I supposed it was an old use or it fell into disuse. So I checked the Ngram on google and it confirmed what Billare said and what I was thinking.