The phrase "a main portion of" is correct and usable in written English.
It can be used when referring to a significant or primary part of something, often in discussions or analyses.
Example: "A main portion of the budget will be allocated to marketing efforts this year."
Alternatives: "a significant part of" or "a primary section of".
The hemispherical hydraulic cylinder also functions as a main portion of crown.
Last week, after a main portion of the first phase of construction was completed, the installation was subjected to load testing, which involved scattering 350 sandbags weighing 50 pounds each and leaving them there for 24 hours.
Hundreds of athletes from quarterback Drew Brees, to Olympic Swimmer Christine Magnusson, and UFC athlete Brandon Vera all use bodyweight exercise as a main portion of their exercise routine.
In this view, small graphics for each slide will appear on the left side of the screen and the currently selected slide will appear in a larger main portion of the screen.
It is then followed by a late receptor potential (LRP) after a 2 ms delay which forms the main portion of the a-wave and is a corneo-negative wave.
I'm not a fan of velcro securing the main portion of a pack, but the Bravo's velcro roll top didn't drive me crazy, though that feat did require thoughtful packing.
The 2009 filing contained a description of podcasting as an outcome of the main portion of the patent, which remained unchanged.
♥ Content: This is the main portion of a yoga class.
Although ochre was found in a variety of contexts on-site, the first burial event (Burial B) in Grave I represents the only dense and continuous concentration of red ochre, as both small chunks and as a continuous layer underlying the main portion of the burial (Figure 3).
The type B genital appendage at first glance appears to be composed of two units, a proximal dorsal segment and an underlying lamella that comprises the main portion of the appendage; however, closer study reveals that these are, in fact, internal structures, and that the true ventral lamella has broken off near its base in both specimens.
Speaker J. Dennis Hastert of Illinois called on Republicans today to develop and enact a plan to pay off the main portion of the debt -- the $3.6 trillion in Treasury bonds owned by the public -- within 15 years.
