Most items within the game have a certain skill requirement to be used, or in case of skills, to be trained. Those requirements are shown within the "Requirements" tab of the item information window.
The tab shows the directly required skills for the item, while each indentation of skill entry represents the requirement of the parent skill. In the example below, only the skills "Black Ops" and "Minmatar Battleship" are required on the listed levels to fly this ship, all other listed skills are merely the requirements for those skills to be trained:
The following symbols can be found within the skill requirement listing:
- - The skill requirements are not met and the skill has not yet been injected into the characters skill list
- - The character has this skill injected, but the skill has not yet been trained to the required level
- - This skill has been sufficiently trained to fullfill the requirement.
- - You are logged in with a Trial Account and this skill is a skill that can not be trained on Trial Accounts. Your account needs to be activated in order to inject and train this skill once its further requirements have been met.
The sentence "This skill cannot be trained on Trial Accounts" that may appear in a skill description or within tooltips is a general information that will always be present independently of the status of your account. It will not prevent training of the skill on an activated account.
Any skill can be injected into a character on a fully activated account, it will however require its prerequisites to have been met in order for that skill to be trained. An example of this would be a character who injects the Minmatar Destroyer skill but has Minmatar Frigate either missing or at level I. Although they have the Destroyer skill injected, they will be unable to train it until they acquire level III of the Minmatar Frigate skill.
Note that prerequisite skills cannot be removed via skill extractions if dependent skills have been trained. As an example, if a character trained Minmatar Destroyer, they cannot remove skill points from their Minmatar Frigate skill and bring it below the required level III through skill extraction.