Is there any research or thought that a one word menu items will get lost between multi word items? Example below... Will "Events" be less visible to the user? I'm thinking the opposite since it easier to discern a one word item than a multi-word-item.
Topic & Tools | Membership & Volunteering | Events | Professional Development
It really depends on how you differentiate the buttons/Keywords. There is a high probability that the smaller words may be considered a part of the bigger phrase (I had conducted usability testing for a similar issue) but to make sure that doesn't happen, having proper spacing differentiating the terms would be highly helpful.
generally speaking I don't think that this will be a problem. The only way for your menu items to get lost is if your spacing is not solid. Make sure that you have enough space between items so that each item is clearly visible as a standalone item. Spacing is crucial.
Should you run into problems with spacing, using a "|" or a dot or any kind of symbol will help the user distinguish the menu items.
I hope this is helpful!
You can always nake that option longer; Events and conventions. Events and presentations. Events and trade shows.
Alternatively, try shortening the others; Solutions Members Events Trainings
(Keep in mind I don't know your company so these suggestions might be way, way off)
