Prime things are usually at the top of their categories. For example, there are prime cuts of meat, primetime TV and prime seats. The movie “Prime” is not one of those things.

In “Prime,” Uma Thurman and Bryan Greenberg play Rafi Gardet and David Bloomberg, two people in the primes of their respective lives. They meet through a mutual friend and quickly find they share an attraction to each other. The big problem is she’s 37 and he’s 23.

Naturally, Gardet takes this concern, with all of her other problems, to her psychiatrist, Lisa Metzger, played by Meryl Streep. Metzger has been helping Gardet through her recent divorce, so she’s thrilled to hear she has a new man in her life.

As Gardet and Bloomberg progress from casual dating to serious commitment, Metzger becomes more privy to the intimate details of their lives. The kicker is, in case anyone has missed the spoiler in the trailer or commercial, this becomes an uncomfortable issue for Metzger as she realizes the new wonder man is none other than her own son.

Should she continue the sessions since her patient is now involved personally with not only her son, but her as well? Despite a conflict of interest Metzger presses on, and it is hilarious to watch Streep’s reactions as she is forced to remain silent while Gardet recounts extremely private moments of her love life.

In a way, “Prime” is all about perspective, especially if seen from Metzger’s point of view. She is involved in both sides of her son’s relationship with Gardet.

On one hand, it is strictly business between her older client and a younger male. On the other hand, it’s personal because her 23-year-old Jewish son is dating a 37-year-old divorcee who is outside the faith.

And herein lies the problem. On some level, the movie is as much about the relationship between Metzger and Gardet as it is about Gardet and Bloomberg. It can’t quite decide if it wants to be a romantic comedy with Streep’s character as a quirky sidekick, or if it really wants to be a comedy with a little romance on the side.

If the main part of the film is about whether the relationship should work, then it’s a romantic comedy. Sure, they have a great time together, but can they overcome their obstacles to be a couple? If the movie is more about the characters’ backgrounds and how those will determine their success or failure in the relationship, however, then it’s a comedy.

Can Metzger accept Rafi as her son’s girlfriend rather than her patient, or will age and religion prove too much for them? It is a very fine line, but it’s one that must be established, and “Prime” never quite gets there.

“Prime” has its funny moments, but most of the time it is confused in its focus and seems lost. Perhaps this is because the ending is vague and never resolves questions to explain why it ends the way it does. Although the actors play well off of each other, “Prime” is a movie far from being at its peak.