A line placed underneath a piece of text in order to provide emphasis or to indicate that it should be viewed in italics or (in electronic documents) that it acts as a hyperlink.
Dated An announcement of a theatrical performance to follow, placed in an advertisement for the current one.
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Dated A caption beneath a photograph (which may have more than one line of text).
Several readers [...] write to point out that the ex-Great Eastern 0-6-0s now classified as "J20" in the L.N.E.R. lists, no longer hold the supremacy for power among British 0-6-0 locomotives as suggested in the underline to the photograph of one of them which appeared on p. 100 of the March-April issue.1944 May and June, “Notes and News: The Most Powerful 0-6-0”, in Railway Magazine, page 186:
underline
verb
Etymology From under- + line.
1
To draw a line underneath something, especially to add emphasis.
The Midlanders will hope the victory will kickstart a campaign that looked to have hit the buffers, but the sense of trepidation enveloping the Reebok Stadium heading into the new year underlines the seriousness of the predicament facing Owen Coyle's men.2011 December 10, Marc Higginson, “Bolton 1 - 2 Aston Villa”, in BBCSport:
By mere chance in appearance, though underlined with a providence, they had a full light of the infanta.1642, Henry Wotton, The Life and Death of the Duke of Buckingham:
Just as it was sometimes necessary to lower the road to take it beneath an underline bridge, so in this case it might be necessary to raise it.1950, Leonora Fry, C. W. Huxtable, Get to know: British railways, page 26:
A minute was saved by smart working at Ipswich, but soon after came yet another delay, a 10 m.p.h. slack over an underline bridge being reconstructed between Bramford and Claydon.1960 June, Cecil J. Allen, “Locomotive Running Past and Present”, in Trains Illustrated, page 369:
1 more example
As to underbridges, the policy is to wait until the small underline bridges become due for renewal when they will be replaced by prestressed concrete structures.1979 August, Michael Harris, “A line for all reasons: the North Yorkshire Moors Railway”, in Railway World, page 412: