Avoid "stretching" for part of a line of justified text

Don't use Shift+Enter to end a line of text.  Use just the Enter key.

In the following text, Shift+Enter was used to terminate the third line of text, while just Enter was used to terminate the sixth line

Your problem is that you are using 2003. That version defaults to using a very brain dead stupid method of "justification" (aligning both margins). It inserts full spaces between words to do the justification. "Real" justification inserts space between words and letters, in "fractional" amounts, not just full space characters. Microsoft was lazy when they tried to copy a feature from WordPerfect, the market leader at the time (1980's).

I don't have access to 2003, but go into Options >Advanced > scroll down to bottom, Layout Options.  Look through the long list of options. Find one that says "Do full justification the way WordPerfect does ..." It may or may not be there. If you find it, turn it on.

https://word.tips.net/T000233_Getting_Rid_of_Choppiness_in_Justified_Text.html

Select the words

Launch the Font dialog

Click on the Advanced tab

Condense the spacing between letters

In this example I applied the condensed spacing then re-opened the Font dialog to show the effect. You won't see it in the body while making the change in the dialog, and the example shown in the preview window will be distorted.

Here is what the line looks like without the condensed spacing

If there are not enough words to fill the line with the normal space between each word, you cannot avoid having space at the end of that line.

Many thanks for the information! Both answers seem like they ought to work, but both present problems. It might be that I’m using Word 2003.

Using return at the end of the line does make everything preceding it flow with normal spacing; but it also indents the end of that line with a substantial space before the following line—so basically it's no longer justified. Using shift + space gives a space at the beginning of the next line.

Using condensed spacing under the font dialog does push things together better. However, the primary place I want to use this is on an often-recurring double space following a number and period. I want the double space both for appearance and for searches. Is there any way to keep its appearance consistent? With justified text it sometimes gives the “right” amount of space, and sometimes at least twice as much. I’m not as concerned about distorted spacing in the rest of the justified text, but it seems to do an inordinately large stretch on the double space.

Thanks again for your kind help!

Select the words

Launch the Font dialog

Click on the Advanced tab

Condense the spacing between letters

In this example I applied the condensed spacing then re-opened the Font dialog to show the effect. You won't see it in the body while making the change in the dialog, and the example shown in the preview window will be distorted.

Here is what the line looks like without the condensed spacing